Evaluation of dosage forms

EVALUATION OF DOSAGE FORMS

1. Solid dosage forms

1.1. Tablets

1.1.1. General appearance

1.1.2. Weight variation

1.1.3. Content uniformity

1.1.4. Mechanical strength of tablets

1.1.5. Disintegration

1.1.6. dissolution

1.2. Effervescent tablets

1.2.1. Effervescent tablets

1.2.2. Water content and moisture uptake studies

1.3. Buccal tablets

1.3.1. Determination of residence time

1.3.2. Swelling studies

1.4. Orally disintegrating tablets

1.4.1. Wetting time

1.4.2. Disintegration time

1.5. Sustained controlled dosage forms

1.5.1. Swelling index study

1.6. Capsules

1.6.1. Stablility tests

1.6.1.1. Shell integrity test

1.6.1.2. Determination of shelf life

1.6.2. Invariability tests

1.6.2.1. Weight variation

1.6.2.2. Content uniformity

1.6.3. Disintegration test

1.6.4. Dissolution test

1.6.5. Moisture permeation test

1.7. Granules

1.7.1. Flow properties

1.8. Powders

1.8.1. Particle size analysis

1.8.2. Angle of repose

1.8.3. Bulk density

1.8.4. Tapped density

1.8.5. Hausner’s ratio

1.8.6. Flowability

2. Semi solid dosage forms

2.1. Ointments

2.1.1. Test of rate of absorption

2.1.2. Test of non-irritancy

2.1.3. Test of rate of penetration

2.1.4. Test of rate of drug release

2.1.5. Test of rheological properties

2.1.6. Test of content uniformity

2.1.7. Test of preservative efficacy

2.2. Creams

2.2.1. Rheology

2.2.2. Sensitivity

2.3. Suppositories

2.3.1. Appearance

2.3.2. Physical strength

2.3.3. Melting range

2.3.4. Uniformity of drug content

2.3.5. Softening time

3. Liquid dosage forms

3.1. Non-sterile liquid dosage forms

3.1.1. Syrups

3.1.1.1. Transmittance of light

3.1.1.2. Visual inspection

3.1.1.3. pH measurement

3.1.1.4. sucrose concentration

3.1.1.5. physical stablility in syrups

3.1.2. Elixirs

3.1.2.1. Determination of alcohol content

3.1.2.2. Viscosity measurement

3.1.3. Suspensions

3.1.3.1. Sedimentation method

3.1.3.2. Rheological method

3.1.3.3. Electrokinetic method

3.1.3.4. Micromeritic method

3.1.3.5. Freeze-thaw test

3.1.3.6. pH measurement

3.1.3.7. visual inspection

3.1.4. emulsions

3.1.4.1. Determination of particle size and particle count

3.1.4.2. Determination of viscosity

3.1.4.3. Determination of phase separation

3.1.4.4. Determination of electrophoretic properties

3.1.4.5. Electrical conductivity

3.2. Sterile liquid dosage forms

3.2.1. Parenterals

3.2.1.1. Leaker test

3.2.1.2. Pyrogen test

3.2.1.3. Sterility test

3.2.1.4. Particulate evaluation

3.2.1.5. Weight variation or uniformity of content

3.2.2. Eye drops

3.2.2.1. Test for sterility

3.2.2.2. Test for ocular toxicity and irritation

3.2.2.3. Test for preservative efficacy

3.2.2.4. Clarity

3.2.2.5. pH

3.2.2.6. In vitro diffusion studies

3.2.2.7. Determination of viscosity

4. Aerosols

4.1. Flammability and combustibility

4.1.1. Flash point

4.1.2. Flame projection

4.2. Physico chemical characteristics

4.3. Performance

4.3.1. Aerosol valve discharge rate

4.3.2. Spray patterns

4.3.3. Dosage with metered valves

4.3.4. Net contents

4.3.5. Foam stability

4.3.6. Particle size determination

4.4. Biological testing

5. Nasal spray

5.1. Appearance, color and clarity

5.2. Drug content

5.3. Impurities and degradation products

5.4. Preservative and stablilizing excipient assay

5.5. Pump delivery

5.6. Spray content uniformity

5.7. Spray content uniformity through container life

5.8. Droplet size distribution

5.9. Foreign particulates

5.10. Microbial limits

5.11. Preservative effectiveness

5.12. Net content and weight loss (stability)

5.13. Leakage testing

5.14. pH

5.15. osmolality

6. Cosmetics

6.1. Lipsticks

6.1.1. Surface anomalies

6.1.2. Thixotropic characters

6.1.3. Breaking point

6.1.4. Melting point

7. Novel drug delivery systems

7.1. Transdermal patches

7.1.1. Thickness

7.1.2. Uniformity of weight

7.1.3. Drug content determination

7.1.4. Content uniformity test

7.1.5. Moisture content

7.1.6. Moisture uptake

7.1.7. Flatness

7.1.8. Tensile strength

7.1.9. Peel adhesion properties

7.1.10. Tack properties

7.1.11. Thumb tack test

7.1.12. Rolling ball test

7.1.13. Quick stick test

7.1.14. Probe tack test

7.1.15. Shear strength properties

Drug substance are seldom administer alone; rather they are given as part of formulation in

combination with one or more non-medicinal agents that serve varied and specialized

Pharmaceutical functions. Selective uses of non medicinal agent referred to as

pharmaceutical ingredients or excipients, produces dosage form of various types.

EVALUATION OF DOSAGE FORMS:

1.SOLID DOSAGE FORMS:

Solid dosage forms are substances having definite shape and volume manufactured for the

administration of active and /or inert ingredient. Solids include tablets, capsules, granules,

powders etc…

1.1. EVALUATION OF TABLETS

Definition: These are solid dosage forms of medicaments which are prepared by moulding

or by compression with or without excipients.

TABLET EVALUATION:

Introduction

1.1.1. General appearance

i. Size and shape

ii. Organoleptic characters or properties

1.1.2. Weight variation

1.1.3. Content uniformity

1.1.4. Mechanical strength of tablet

i. Hardness

ii. Friability

iii. Tensile strength

1.1.5. Disintegration test

1.1.6. Dissolution test

Why to evaluate tablets?

To monitor the product quality.

For quantitative evaluation and assessment of tablet properties

To check chemical breakdown.

To check the interactions between physical components of tablets.

1.1.1. General appearance:

i. Size and shape:

Tablet thickness varies with changes in-

a) Die fill

b) Particle size distribution and

c) Packing of the powder mix being compressed and with tablet weight.

The thickness of tablet is measured with a micrometer tablet thickness should be controlled

within a +-5% variation of a standard value.

ii. Organoleptic properties:

Color (no mottling)

Odour (e.g. film coated tablets)

Taste (e.g. chewable tablets)

1.1.2. Weight variation:

Twenty tablets were selected randomly from each batch and weighed individually to check

for weight variation.

The USP has provided limits for the average weight of uncoated compressed tablets.

I.P Average weight (mg) USP % difference

Less than 85 130 mg or less 10

85-324 >130 mg but <324 mg 7.5 324 or more 324 mg (or) more 5

1.1.3. Content uniformity:

Every tablet contains the amount of drug substances intended with little variation among

tablets within a batch.

For content uniformity test, representative samples of 30 tablets are selected and 10 are

assayed individually. Nine of the 10 tablets must contain NLT 85 % or more than 115% of the

labeled drug content.

The three factors that directly contribute to content uniformity problems:

i. Non-uniformity distribution of drug substance throughout the powder

mixture or granulation.

ii. Segregation of powder mixture or granulation during various manufacturing

processes.

iii. Tablet weight variation.

1.1.4. Mechanical strength of tablets:

It provides a measure of the bonding potential of the material concerned and this

information is useful in the selection of excipients.

The excessively strong bonds prevent rapid disintegration and subsequent dissolution.Can

be quantified by

i.friability

ii. Hardness

iii. Tensile strength

i. Friability:

The friability test is closely related to tablet hardness and is designed to evaluate the

ability of the tablet to withstand abrasion in packaging, handling and shipping. It is

measured by the use of Roche friabilator.

Method:

A number of tablets (say 20) are weighed and placed in the apparatus where they are

exposed to rolling and repeated shocks as they fall 6 inches in each turn within the

apparatus.

After four minutes of this treatment or 100 revolutions, the tablets are weighed and

the weight compared with the initial weight.

The loss due to abrasion is a measure of the tablet friability. The value is expressed as a

percentage.

A maximum weight loss of NMT 1% of the weight of the tablets being tested during the

friability test is considered generally acceptable and any broken or smashed tablets or

not picked up.

ii. Hardness:

Hardness or crushing strength determinations are made during tablet

production, are used to determine the need for pressure adjustment on tablet

machine. The force required to break the tablet is measured in kilograms and a

crushing strength if 4 kg is usually considered to be the minimum for satisfactory

tablets. Oral tablets have 4 to 10 kg hardness. Hypodermic and chewable tablets

are usually much softer (3kg) and some sustained release tablets are much

harder (10-20 kg). Tablet hardness had been associated with other tablet

properties such as density and porosity.

Hardness of the tablets can be determined by using following apparatus:

Stokes hardness tester

Strong-cobb apparatus

Schleuniger apparatus

iii. Tensile strength:

This is the force required to break a tablet in a diametric compression test. The

radial tensile strength, T, of the tablets can be calculated from the equation:

T=2F/∏dH

Where F is the load needed to break the tablet, d and H are diameter and

thickness respectively. It is determined by static and dynamic methods.

1.1.5. Disintegration:

For a drug to be absorbed from a solid dosage form after oral administration, it must first be

in solution, and the first important step toward this condition is usually the break-up of the

tablet; a process known as disintegration.

The disintegration test is a measure of the time required under a set of conditions for a

group of tablets to disintegrate into particles which will pass through a 10 mesh screen.

The disintegration test is carried out using the disintegration tester which consists of a

basket rack holding 6 plastic tubes, open at the top and bottom, the bottom of the tube is

covered by a 10 mesh screen.

The basket is immersed in a bath of suitable liquid held at 37°C, preferably in a 1L beaker.

For most uncoated tablets, the BP requires that the tablets disintegrate in 15 minutes

(although it varies for some uncoated tablets) while for coated tablets, up to 2 hrs may be

required. To test for disintegration time, one tablet is placed in each test tube and basket

rack is positioned in a 1L beaker of water, simulated gastric fluid at 37°c ±2°c, such that

tablets remain 2.5 cm below the surface of liquid on their upward movement. A standard

motor driven device is used to move the basket assembly, at a frequency of 28-32

cycles/min. To be in USP tablets=5 min (aspirin tablets). Majority of tablets have a

disintegration time of 30 minutes. Enteric coated tablets = 2hrs + time specified in

monograph (simulated intestinal fluid).

TYPE OF TABLETS DISINTEGRATION TIME DISINTEGRATION MEDIA

UNCOATED TABLETS 15 min Water

SOLUBLE TABLETS 3 min Water

DISPERSIBLE TABLETS 5 min Water

EFFERVESCENT TABLETS 5 min Water

SUGAR COATED TABLETS 60 min Water / 0.1 M Hcl

FILM COATED TABLETS 30 min Water

ENTERIC COATED TABLETS

120 min Water / 0.1 M Hcl

1.1.6. DISSOLUTION:

Dissolution is the process by which a solid solute enters a solution. Pharmaceutically, it may

be defined as the amount of drug substance that goes into solution per unit time under

standardized conditions of liquid/solid interface, temperature and solvent composition.

Dissolution kinetics is important in determining the bioavailability of a drug. Two objectives

in the development of in-vitro dissolution tests are to show;

1. That the release of the drug from the tablet is as close as possible to 100%

2. That the rate of drug release is uniform batch to batch

Thus we can say that,

Rate of dissolution is directly proportional to efficacy of product

Rate of dissolution is directly proportional to bioavailability

It is carried out in apparatus which are given below:

TYPE OF APPARATUS

I.P B.P E.P USP

TYPE-1 Paddle apparatus

Basket apparatus

Paddle apparatus

Basket apparatus

TYPE-2 Basket apparatus

Paddle apparatus

Basket apparatus

Paddle apparatus

TYPE-3 Flow through cell apparatus

Flow through cell apparatus

Reciprocating cylinder type apparatus

TYPE-4 Flow through cell apparatus

TYPE-5 Paddle over disc

TYPE-6 Rotating cylinder type

TYPE-7 Reciprocating type of apparatus

In general a simple tablet is placed in a small wire mesh basket fastened. To the bottom

of the shaft connected to a variable speed motor.

The basket is immersed in the dissolution medium (as specified in the monograph)

contained in a flask. The flask is maintained at constant temperature of 37°c +- 5°c by a

constant temperature bath.

The motor is adjusted to turn at the specified speed and samples of fluid are withdrawn

at intervals to determine the amount of drug in solution1.

SPECIFIC TESTS:

1.2. EFFERVESCENT TABLETS

Effervescent tablets are uncoated tablets that generally contain acid substances and

carbonates or bicarbonates and that react rapidly in the presence of water by releasing CO 2

EVALUATION:

1.2.1. EFFERVESCENT TIME:

Place one tablet in a 250ml beaker containing water at 20°c to 30°c numerous gas bubbles

are evolved. When the evolution of gas around the tablet or its fragments has ceased the

tablet shall have disintegrated being either dissolved or dispersed in the water so that no

agglomerates of particles remain.

Repeat the operation on a further 5 tablets. The tablets comply with the test if each of the 6

tablets disintegrates in the manner prescribed within 5 minutes (I.P. 2007).

1.2.2. WATER CONTENT AND MOISTURE UPTAKE STUDIES:

Three tablets were exposed to three different humidity conditions at 23°c. Controlled

humidity chambers (31%, 45% & 79.3% RH) were constructed using various saturated salt

solutions in desiccators.

The 31% RH desiccators contained a saturated solution of CC the 45% RH contained

ammonium chloride. Tablets were subjected to these humidities for approximately 60 days.

Moisture studies check by Karl fischer method2.

1.3. BUCCAL TABLETS

Buccal medications are administered by placing them in the mouth between the gum and

the cheek. These medications dissolve rapidly and are absorbed through the mucous

membranes of the mouth where they enter into the blood stream.

Parameters of evaluation:

1) Determination of residence time

2) Permeation studies

3) Swelling studies

4) Release rate studies

5) Toxicity and irritation study

6) Bioadhesion measurement

7) Content uniformity

1.3.1. DETERMINATION OF RESIDENCE TIME:

DETERMINATION OF RESIDENCE

TIME

INVITRO RESIDENCE TIME

INVIVO RESIDENCE TIME

INVITRO RESIDENCE TIME:

For this test we use the USP dissolution test apparatus. Composition of dissolution

medium=800ml isotonic phosphate buffer solution.

A segment of rabbit buccal mucosa, 3cm long, is glued to the surface of a glass slab. Whichis

vertically attached to the apparatus.

The mucoadhesive tablet is hydrated from one surface using 15ml IPB and then the

hydrated surface is brought into contact with the mucosal membrane.

The glass slab is vertically fixed to the apparatus and allowed to move up and down so that

the tablet is completely immersed in the buffer solution at the lowest point and is out at the

highest point.

The time necessary for complete erosion or detachment of the tablet from the mucosal

surface is recorded.

IN VIVO RESIDENCE TIME:

Plain bioadhesive tablets with optimized properties are selected for the evaluation.

Procedure:

The bioadhesivetablets is placed on the buccal mucosa between the check and gingival in

the region of the upper canine and gently pressed onto the mucosa for about 30 seconds.

The tablet and the inner upper lip are carefully moistened with saliva to prevent the sticking

of the tablet to the lip. The time necessary for complete erosion of the tablet is

simultaneously monitored by carefully observing for residual polymer on the mucosa. In

addition, any complaints such as discomfort, bad taste, dry mouth, or increase of salivary

flux, difficulty in speaking, irritation or mucosal lesions are carefully recorded. Repeated

application of the bioadhesive tablets is allowed after a two days period for the same

volunteer.

1.3.2. SWELLING STUDIES:

Buccal tablets are weighed individually (W1) and placed separately in 2% agar gel plates with

the core facing the gel surface and incubated at 37± 0.1°c . The tablet was removed from

the petri dish and excess surface water is removed carefully using filter paper. The swollen

tablet is then reweighed (W2), and the swelling index (SI) or percent hydration is calculated

using the following formula3,

% of hydration = (W2-W1)×100/W2

W1 = initial weight of tablet

W2 = weight of disk at time t

1.4. ORALLY DISINTEGRATING TABLETS:

An orally disintegrating tablet or orodispersible tablet (ODT) is a drug dosage form available

for a limited range of over-the-counter (OTC) and prescription medications. ODTs differ

from traditional tablets in that they are designed to be dissolved on the tongue rather than

swallowed whole.

1.4.1. Wetting time :

Wetting time of dosage form is related to the contact angle. It needs to be assessed to give an insight into the disintegration properties ofWetting time of dosage form is related to the

contact angle. It needs to be assessed to give an insight into the disintegration properties of the tablets; a lower wetting time implies a quicker disintegration of the tablet. For this

purpose, a tablet is placed on a piece of tissue paper folded twice and kept in a small Petri dish (ID = 6.5 cm) containing 6 ml of water,and the time for complete wetting is measured.

1.4.2. Disintegration time:

The time for disintegration of ODTs is generally less than one minute and actual disintegration time that patient can experience ranges from 5-30 seconds. The standard procedure of performing disintegration test for these dosage forms has several limitations

and they are not suitable for the measurement of very short disintegration times. The method needs to be modified for ODTs as disintegration is required without water; thus the test should mimic disintegration in salivary contents. A modified dissolution apparatus is applied to an ODT with a disintegration time that is too fast to distinguish differences between tablets when the compendial method is used. A basket sinker containing the

tablets is placed just below the water surface in a container with 900 mL of water at 37 0C, and a paddle rotating at 100 rpm is used. The disintegration time is determined when the tablet has completely disintegrated and passed through the screen of the sinker404.

1.5. SUSTAINED CONTROLLED RELEASE DOSAGE FORMS

In sustained release concentration will be vary with time interval because in case of sustained

release initial release of drug sufficient to provide a therapeutic dose soon after

administration & then gradual release over an extent period. While in case of

controlled release dosage formrelease drug at a constant rate ...

1.5.1. Swelling index study:

The extent of swelling was measured in terms of percentage weight gain by the tablet. The

swelling behaviour of all formulation was studied. One tablet from each formulation was kept

in a petri dish containing pH 7.4 phosphate buffers. The tablet was removed every three hour

interval up to 12 hour and excess water blotted carefully using filter paper. The swollen

tablets were re-weighed (W2). The swelling index (SI) of each tablet was calculated

according to the following equation .S.I. = {(Wt-W0) / W0} ×100 Where- W0 = initial

weight, Wt = final weight5.

1.6. EVALUATION OF CAPSULES

Capsule is a solid dosage form in which the drug is enclosed in a hard or soft soluble

container, usually of a form of gelatin.

Following tests are carried out for the evaluation of capsules:

1.6.1. STABILITY TESTS

1.6.1.1. Shell integrity test

1.6.1.2. Determination of shelf life

1.6.2. INVARIABILITY TESTS

1.6.2.1. weight variation

1.6.2.2. Content uniformity

1.6.3. DISINTEGRATION TEST

1.6.4. DISSOLUTION TEST

1.6.5. MOISTURE PERMEATION TEST

1.6.1. STABILITY TESTS:

Stability tests for capsules are performed to know the integrity of gelatin capsule

shell (but not to known the stability of therapeutically active agent) and for

determining the shelf life of capsules. The test helps in improving the quality of

contents of capsule shell and for choosing the appropriate retail package.

Before actually performing the tests following fact:

The capsule shell are to be stabilized to know atmospheric condition with relative

humidity about 20-30% and temperature about 21-24⁰c.

a) Shell integrity test:

This test is performed to find out the integrity of capsule shell. The standard

capsule shells kept at the room temperature 40⁰c and 80% RH becomes more soft,

sticky and swollen.

b) Determination of shelf life:

Shelf life or the expiry date of packed capsules is determined under normal

storage conditions.

1.6.2. Invariability tests:

The invariability in the medicaments packed in the capsule shells can be

determined by performing the following tests:

a) Weight variation test

b) Content uniformity test

1.6.3. DISINTEGRATION TEST:

Disintegration test is a method to evaluate the rate of disintegration of solid dosage

forms. Disintegration is defined as the breakdown of solid dosage form into small

particles after it is ingested.

1.6.4. DISSOLUTION TEST:

Dissolution test is an official method to determine the dissolution rate of a solid

dosage form. Dissolution rate is defined as the rate at which the drug is released into

the systemic circulation from the dosage form.

Dissolution test apparatus:-

a) Apparatus-I (rotating basket dissolution apparatus):

Small wire mesh size basket – 22

Temperature - 37±5⁰c

Rotated speed – 25-150rpm

Dissolution medium height from the bottom of the vessel – 23-27mm.

b) Apparatus-2 (rotating paddle dissolution apparatus):

Small wire mesh size: 22

Dissolution medium height from the bottom of the vessel – 23-27mm

Temperature - 37±5⁰c

Rotated speed – 25-150rpm

1.6.5. Moisture permeation test:

This test is carried out to assure the suitability of containers for packaging of

capsules. The moisture permeating feature of capsules packaged in

Single unit containers-blister pack or strip pack.

Unit dose containers glass or plastic bottle is to be determined6.

1.7. EVALUATION OF GRANULES

Definition: Granules are multi particle entities in which primary powder particles are made

to adhere to form larger particle. Granules size range between 0.2 to 4 mm. In tablets and

capsules, granules are the intermediate product and having size of 0.2 to 0.5 mm.

1.7.1. Flow properties:

It is an ability of the granule to flow from hopper to die cavity for tablet uniformity. Flow

properties of granules are not uniform and then it leads to not getting tablet of uniform size.

Flow property of material results from many forces.

1. Frictional force

2. Surface tension force

3. Mechanical force caused by interlocking of irregular shape particles.

4. Electrostatic forces

5. Cohesive/vanderwaals forces

Forces also affect granule property such as particle size, particle size distribution, particle

shape, surface texture, roughness and surface area. If particle size of powder is ≤ 150 µm

the magnitude of frictional and vanderwaals force predominate. When particle size

increases mechanical and physical properties become more important with packing

properties.

In fig.(1) height is constant and powder is added through the hopper until

powder reaches tip of funnel.

In fig.(2) height is varied and base cone is fixed, powder is added until height

reaches at max.

In fig.(3) rectangle box is filled with powder and tipped until content begins

to slide.

In fig.(4) revolving cylinder with transparent end is made to revolve

horizontally when half filled with powder.

The maximum angle that the plane of powder makes with horizontal surface

on rotation is taken as the angle of repose.

(1),(2) & (3) gives static angle of repose. While (4) gives kinetic or dynamic

angle of repose7.

1.8. EVALUATION OF POWDERS

Powders are subdivided solids which are classified according to the size of their constituent

particles which range from <1.25 micrometer to 1.7mm

Classification of Powders:

1.Bulk powders

2.Divided powders

3.Dusting powders

4.Insufflations

Evaluation parameters to be performed are:

1.8.1. Particle size analysis

1.8.2. Angle of repose

1.8.3. Bulk density

1.8.4. Tapped density

1.8.5. Hausner’s ratio

1.8.6. Flowability

1. Particle Size Analysis:

The powders have been classified into:

As per vegetable & animal origin:

Very Coarse(#8): All particles pass through sieve no.8 and not more than 20% through sieve

no.20

Coarse (#20): all particles pass through sieve no.20 not more than 40% through sieve no.60

Moderate(#40): All particles pass through sieve no.40 and not more than 40% through s ieve

no.60

Fine(#60): All particles pass sieve no.60 and not more than 40% through sieve no.80

Very Fine: All particles pass through this sieve. There is no limits as to greater fineness.

Powders of chemical drugs are classified as:

Coarse (#20): All particles pass through sieve no.20 not more than 40% through sieve no.60

Moderate(#40): All particles pass through sieve no.40 and not more than 40% through sieve

no.80

Fine(#60): All particles pass sieve no.60 and not more than 40% through sieve no.80

2.Powder Flowability:

Powder flowability is the ability of powder to flow in a desired manner in a specific piece of

equipment.

Flow of powders may be:

• Free flowing

• Non-flowing or cohesive.

Flow Patterns:

• Funnel Flow

• Mass Flow

Measurement of flow property:

Powder Rheometer

Cohesive index

Flow through Orifice

Carr’s Index &Hausner’s ratio

Angle Of Repose

penetrometry

Angle of Repose:

The internal angle between the surface of the pile and height of the pile.

Θ=Tan-1(h/r)

It depends upon:

• Density

• Surface area

• Shape of the particles

• The coefficient of friction of material

Flow property Angle of repose(degrees)

Excellent 25-30 Good 31-35 Fair-aid not needed 36-40 Passable-may hang up 41-45 Poor-must agitate, vibrate 46-55 Very poor 56-65 Very, very poor >66

Carr’s Index &Hausner’s Ratio:

Both are determined by measuring bulk volume and tapped volume of powder.

Compressibility index(%) Flow character Hausner ratio

10 Excellent 1.00-1.11 11-15 Good 1.12-1.18

16-20 Fair 1.19-1.25 21-25 Passable 1.26-1.34 26-31 Poor 1.35-1.45 32-37 Very poor 1.46-1.59 >38 Very, very poor >1.60

Flow Through An Orifice:

• Useful only for free flowing powders.

Types Of flow Rate:

• Mass flow rate: Quantity of powder flow per minute.

• Volume flow rate: Time taken by the powder in a container to drain out.

COHESION INDEX:

• Determined by integrating the negative areas under force displacement curve.

Cohesion index (mm) = cohesion co-efficient (g,mm) / sample weight (g)

A low cohesion index is associated with non-cohesive free flowing powders

Cohesion index Flow behaviour

≥19 Hardened, extremely cohesive 16-19 Very cohesive 14-16 Cohesive 11-14 Easy flowing ≤11 Free flowing

POWDER RHEOMETER:

The forces causing deformation of powders is measured here.

This gives measurement of:

• Flow energy

• Shear properties

• Bulk properties

PENETROMETRY:

The pressure of penetration in pascal was used to estimate flow rate.

Particle size should be in the range of:

0.250-0.630 mm

Especially used for non-consolidated pharmaceutical powder excipients:

• Sodium chloride

• Sodium citrate

• Boric acid

• Sorbitol7

2. SEMI SOLID DOSAGE FORMS

Semi solids are the topical dosage form used for the therapeutic, protective or cosmetic

function. They may be applied to the skin, or used nasally, vaginally, or rectally.

Semi solid dosage forms include ointments, creams, suppository, aerosols, transdermal drug

delivery systems, gels, paints, lotions, etc…..

2.1.EVALUATION OF OINTMENTS

Ointments are semisolid dosage forms in which are or more drug substances are

dissolved or dispersed or emulsified in a suitable ointment base and are meant for

application on skin or mucous membrane where it for application on skin or mucous

membrane where it exhibit local or systemic effects.

The different methods of evaluation of ointments are:

2.1.1. Test of rate of absorption

2.1.2. Test of non-irritancy

2.1.3. Test of rate of penetration

2.1.4. Test of rate of drug release

2.1.5. Test of rheological properties

2.1.6. Test of content uniformity

2.1.7. Test of preservative efficacy.

2.1.1. TEST OF RATE OF ABSORPTION:

The diadermatic ointment should be evaluated for the rate of absorption of drug

into the blood stream.

This test can be done in-vivo only. The ointment should be applied over a definite

area of the skin by rubbing.

At regular intervals of time, serum and urine samples should be analyzed for the

quantity of drug absorbed.

The rate of absorption i.e., the amount of drug absorbed per unit time should be

more.

2.1.2. TEST OF NON-IRRITANCY:

The bases used in the formulation of ointments may cause irritation or allergic

reactions. Non-irritancy of the preparation is evaluated by patch test.

In this test 24 human volunteers are selected. Definite quantity of ointment is applied

under occlusion daily on the back or volar fore arm for 21 days.

Daily the type of pharmacological action observed is noted.

No visible reaction or erythema or intense erythema with edema and vesicular

erosion should occur.

A good ointment base shows no visible reaction.

2.1.3. TEST OF RATE OF PENETRATION:

The rate of penetration of a semisolid dosage form is crucial in the onset and duration

of action of the drug. Weighed quantity of the preparation should be applied over

selected area of the skin for a definite period of time. Then the preparation left over

is collected and weighed. The difference between the initial and the final weights of

the preparation gives the amount of preparation penetrated through the skin and this

when divided by the area and tie period of application gives the rate of penetration of

the preparation. The test should be repeated twice or thrice.

2.1.4. TEST OF RATE OF DRUG RELEASE:

To assess the rate of release of medicament, small amount of the ointment can be

placed on the surface of nutrient agar contained in a petri dish or alternately in a

small cup cut in the agar surface. If the medicament is bactericidal the agar plate is

previously seeded with a suitable organism like S.aureus. After a suitable period of

incubation, the zone of inhibition is measured and correlated with the rate of release.

2.1.5. TEST OF RHEOLOGICAL PROPERTIES:

The viscosity of the preparation should be such that the product can be easily

removed from the container and easily applied to the skin. Using cone and plate

viscometer the viscosity of the preparation is determined.

2.1.6. TEST OF CONTENT UNIFORMITY:

The net weight of contents of ten filled ointment containers is determined. The

results should match each other and with the labeled quantity.

2.1.7. TEST OF PRESERVATIVE EFFICACY:

Using pour plate technique the number of micro-organisms initially present in the

preparation are determined. Solutions of different samples of the preparation are

made and mixed with TryptoneAzolectin (TAT) broth separately. All cultures of the

micro-organisms are added into each mixture, under aseptic conditions. All mixtures

are incubated. The number of micro-organisms in each sample will be counted on

7th,14th,21st,and 28th days of inoculation.

MICROBIAL LIMITS:-

On 14th day, the no. of vegetative cells should not be more than 0.1% of initial

concentration.

On 28th day, the number of organisms should be below or equal to initial

concentration8.

2.2. EVALUATION OF CREAMS

As these products are used widely and for various parts of the body, stringent

evaluation and quality control is essential, appearance, spread ability, wash ability.

2.2.1. RHEOLOGY:

Rheology is very important as these creams are marketed in tubes (or) containers. The

rheology or viscosity should remain constant. As these products are normally non-

newtonian in nature, viscosity can be measured using viscometers used for such liquids.

Rheological measurements are utilized to characterize the ease of pouring from a

bottle, squeezing from a tube or other deformable container, maintaining product shape in

a jar or after extrusion, rubbing the product onto and into the skin and pumping the product

from mixing and storage to filling experiment.

2.2.2. SENSITIVITY:

As various types of ingredients are used with occasional use of antiseptics, hormones etc.,

there is a possibility of sensitization or photosensitization of the skin. This should be tested

before hand. This test is normally done by patch test on and can be either open or occlusive.

The test sample is applied along with a standard market product at different places and

effect is compared after a period of time9.

2.3. EVALUATION OF SUPPOSITORIES

A suppository is a drug delivery system that is inserted into the rectum (rectal suppository),

vagina (vaginal suppository) or urethra (urethralsuppository), where it dissolves or melts

and is absorbed into the blood stream.

Suppositories are evaluated for following parameters:

2.3.1. Appearance

2.3.2. Physical strength

2.3.3. Melting range

2.3.4. Uniformity of drug content

2.3.5. Softening time

2.3.1. TEST FOR APPEARANCE:

All the suppositories should be uniform size and shape and should have elegant

appearance. Suppositories should be examined for cracks and pits on the surface of

suppositories.

2.3.2. TEST FOR PHYSICAL STRENGTH:

The strength of the suppositories should be considered to assess their ability during normal

handling. The apparatus used for this is called as breaking test apparatus, which contains a

double walled chamber in which water is pumped to maintain 37°C temperature in between

the two walls of the chamber. The inner chamber contains a disc for holding the

suppositories. To this disc a rod is attached. The other end of the rod contains a disc for

holding the weights. When the weights are added (upto 200gms) at one minute time

interval until the suppositories crumbles. All the weights used are added which gives the

tensile strength. Tensile strength is the maximum force which the suppository can withstand

during production packing and handling. Higher the tensile strength indicates less will be

tendency to fracture.

2.3.3. MELTING RANGE TEST:

Macro melting range – it gives the measure of thermal stability of the suppository. It is the

time taken by the entire suppository to melt in a constant temperature water bath. The test

is conducted using the tablet disintegration test apparatus. The suppository is immersed in a

constant water bath, finally the melting range is recorded.

Micromelting range – the melting range of fatty base is measured by using capillary tubes.

2.3.4. TEST FOR UNIFORMITY OF DRUG CONTENT:

This is carried out by performing assays for different suppositories. All the suppositories

should contain the same labelled quantity.

2.3.5. TEST FOR SOFTENING TIME:

This test measures the softening or liquefaction time of suppository which indicates the

hardness of the base.

Method:

The apparatus consists of cellophane tube tied at the two ends of condenser. The two ends

of the cellophane tube are opened. Water is circulated through the condenser at a definite

rate. As a result after sometime the upper half of the tube opens wide and lower half

collapses. The time period in which the suppository melts completely is considered as

softening time10.

3. LIQUID DOSAGE FORMS

A solution is a liquid preparation that contains one or more soluble chemical substances

dissolved in a specified solvent.

3.1. NON - STERILE LIQUID DOSAGE FORMS

3.1.1. EVALUATION TESTS FOR SYRUPS:

A concentrated solution of a sugar, such as sucrose, in water or other aqueous liquid, somet

imes with amedicinal agent added; usually used as a flavored vehicle for drugs. It is common

ly expanded to include any liquid dosage form (e.g., oralsuspension) in a sweet and viscid ve

hicle.

Following tests are carried out for the evaluation of syrups:

3.1.1.1. Transmittance of light :

A light transmittance meter is a newer tool that is used to check syrup color. In a

light transmittance meter, a syrup sample is checked for color by passing light

through the sample. The percent of light transmission is compared to light

transmission rates set for different grades. When using one, you need to be sure

there are no finger prints on the syrup test bottle, and that the syrup sample has no

bubbles or cloudiness. Any of these conditions may diminish the light that is

transmitted through the sample and therefore lowers the grade of the sample.

3.1.1.2. Visual inspection:

With visual inspection, the ingredients and the final products are carefully examined

for purity and for appearance. Physical appearance of products for patient

adherence and compliance is critical so it should be

Good looking

Elegance in appearance

3.1.1.3. pH measurement:

The measurement and maintenance pH is also very important step in the quality

control testing. Generally there are two different types of methods used in the

measurement of pH.

Methods for pH measurement:

The simplest and cheapest is to dip a piece of pH paper into the sample. The

paper is impregnated with chemicals that change color and the color may be

compared to a chart supplied with the paper to give pH of the sample.

If greatest accuracy is required a pH meter should be used. A typical pH

meter consists of a special measuring glass electrode connected to and

electronic meter that measures and displays the pH reading.

3.1.1.4. Sucrose concentration:

The determination of sucrose concentrations is also very important in quality control

testing of syrups. It the concentration of sucrose in the syrup is very high it may

crystallize the syrup and less sucrose concentrations give favor for the microbial

growth.

There is no specific method for the determination of sucrose in syrup, we use HPLC

and UV- spectroscopy for this purpose.

3.1.1.5. Physical stability in syrups:

The syrups are must be stable physically.

Example:

Its appearance (no crystallization and microbial growth)

Color must be completely soluble with other ingredients

Odour and taste(palatable)

Solid material is completely miscible in liquid11.

3.1.2. EVALUATION OF ELIXIRS

Definition: Elixirs are clear, sweetened hydro alcoholic solutions intended for oral use and

are usually flavoured to enhance their palatability.

Evaluation parameters:

3.1.2.1. Determination of alcohol content:

Elixir usually contains 5 to 40% alcohol.The determination of alcohol unless otherwise

specified in the individual monograph. It is suitable for examining most fluidextracts and

tinctures and elixirs provided the capacity of the distilling flask is sufficient (commonly

two to four times the volume of the liquid to be heated) and the rate of distillation is

such that clear distillates are produced. Cloudy distillates may be clarified by agitation

with talc, or with calcium carbonate. And filtration is done. After which the temperature

of the filtrate is adjusted and the alcohol content determined from the specific gravity.

During all manipulations, take precautions to minimize the loss of alcohol by

evaporation.For Liquids it is presumed to Contain less than 30% of Alcohol.

3.1.2.2. Viscosity measurement:

Viscosity is a property of liquids that is directly related to the resistance to flow.

Viscosity measurement is very important quality control test in case of syrups an elixirs.

Viscosity and consistency directly relates with stability of solutions. If viscosity increases,

then there is a chance of increase in stability11.

3.1.3. EVALUATION OF SUSPENSIONS

A pharmaceutical suspension is a coarse dispersion in which insoluble particles, generally

greater than 1 µm in diameter, are dispersed in a liquid medium, usually aqueous.

Following are the tests are carried out for the evaluation of suspensions:

3.1.3.1. Sedimentation method:

Two parameters are studied for determination of sedimentation. They are:

Sedimentation volume:

The suspension formulation (50ml) was poured separately into 100ml measuring

cylinder and sedimentation volume was read after 1,2,3 and 7 days. And there after

at weekly intervals for 12 weeks. Triplicate results were obtained for each

formulation. Sedimentation volume was calculated according to equation:

F =Vu/Vo

Where, F = sedimentation volume

Vu=ultimate height of sediment

Vo= initial height of total suspension

Degree of flocculation:

Degree of flocculation was calculated according to the equation

β=F/Fα

= flocculated sedimentation volume/deflocculated sedimentation volume

F has values ranging from less than one to greater than one.

Normally F < 1

When F < 1 ↔ Vu <Vo

When F = 1 ↔ Vu <Vo

The system is in flocculated equilibrium and show no clear supernatant on standing.

When F > 1 ↔ Vu >Vo

Higher the value, higher will be the stability.

3.1.3.2. Rheological method:

Viscosity of suspensions is of great importance for stability and pourability of

suspensions. As we know suspensions have least physical stability amongst all

dosage forms due to sedimentation and cake formation.

So as the viscosity of the dispersion medium increases, the terminal settling velocity

decreases thus the dispersed phase settle at a slower rate and they remain dispersed

for longer time yielding higher stability to the suspension.

On the other hand as the viscosity of the suspension increases, it’s pourability

decreases and inconvenience to the patients for dosing increases. Thus, the viscosity

of suspension should be maintained within optimum range to yield stable and easily

pourable suspensions.

A practical rheologic method involves the use of Brookfield viscometer mounted on

a helipath stand. The T-bar spindle is made to descend slowly into the suspension,

and the dial reading on the viscometer is then measure of the resistance the spindle

meets at various levels ina sediment.

Data obtained on samples variously aged and stored indicate whether undesired

changes are taking place. This measurement is made on undisturbed samples of

different ages. The results indicate how the particles are settling with time.

In screening study, the better suspensions show a lesser rate of dial reading with

spindle turns, i.e., the curve is horizontal for a longer period.

3.1.3.3. Electrokinetic method:

In this zeta potential is measured by using micro electrophoresis apparatus and zeta

plus (Brookhaven instruments corporation, USA). It shows the stability of a disperse

system.

Eg: micro-electrophoresis apparatus MK 1

Zeta potential:

The zeta potential of the formulated suspensions was determined using a zetaplus

(Brookhaven instruments corporation, USA). Approximately 1ml of suspension was

transferred into a plastic cuvette using a pipette and diluted with distilled water. The

Brookhaven zeta potential software was used for the measurement. Parameters set

to a temperature of 25⁰c and refractive index (1.33). the zeta potential of the

formulations was determined on day 0,7,14,21 and day 28 post formulation.

3.1.3.4. Micromeritic method:

The stability of suspension depends on the particle size of the dispersed phase.

Change in the particle size with reference to time will provide useful information

regarding the stability of a suspension. A change in particle size distribution and

crystal habit can be studied by microscopy and coulter counter method.

Photo microscopy method:

The microscope can be used estimate and detect changes in particle size distribution

and crystal form. Rapid processing of photo micrographs in enhanced by attaching

polaroid camera to the piece of monomolecular microscope. By using this photo

micrographs we can determine the changes in physical properties and stability of

suspensions.

3.1.3.5. Freeze-thaw test:

Freeze-thaw test conducted by placing the sample in a freezer for 18 hours followed

by thawing at room temperature for 4 to 6 hours. Repeat the freeze-thaw cycle for

10 times. This test is conducted to determine the tendency to crystallize or color.

3.1.3.6. pH measurement:

The measurement and maintenance pH is also very important step in the quality

control testing. Generally there are two different types of methods used in the

measurement of pH.

Methods for pH measurement:

The simplest and cheapest is to dip a piece of pH paper into the sample.

3.1.3.7. Visual inspection:

With visual inspection, the ingredients and the final products are carefully examined

for purity and for appearance. Physical appearance of products for patient adherence and

compliance is critical so it should be:

good looking

Elegance in appearance12.

3.1.4. EVALUATION OF EMULSIONS

An emulsion is a system consisting of two immiscible liquid phases, one of which is

dispersed throughout the other in the form of fine droplets. A third component, the

emulsifying agent, is necessary to stabilize the emulsion.

Following are tests carried out for evaluation of emulsions:

3.1.4.1. Determination of particle size and particle count:

Determination of changes in the average particle size or the size distribution of droplet

is an important parameter used for the evaluation of emulsions. It is performed by optical

microscopy, sedimentation by using Andreason apparatus and coulter apparatus.

3.1.4.2. Determination of viscosity:

Determination of viscosity is done to assess the changes that might take

place during aging. Emulsions exhibit non-newtonian type of flow characteristics.

The viscometer which should be used may be cone and plate viscometer.

3.1.4.3. Determination of phase separation:

This is another parameter used for assessing the stability of the formulation. Phase

Separation may be observed visually or by measuring the volume of the separated phases.

3.1.4.4. Determination of electrophoretic properties:

Determination of electrophoretic properties like zeta potential is useful for assessing

flocculation since electrical charges on particles influence the rate of flocculation.

o/w emulsion having a fine particle size will exhibit low resistance but if the particle

size increase, then it indicates a sign of oil droplet aggregation and instability.

3.1.4.5. Electrical conductivity:

It is determined by using platinum electrodes (diameter 0.4 mm, distance 4mm)

micro amperometrically to produce a current of 15 to 50mA. Measurements are

made on emulsions stored at room temperature or at 37⁰c for short time. Stable o/w

emulsion offer less resistance, but droplet aggregation increases resistance. A stable

w/o emulsion does not conduct electrodes, but with droplet coagulation

conductivity increases13.

3.2. STERILE LIQUID DOSAGE FORMS

3.2.1. EVALUATION OF PARENTERALS

Following tests are carried out for the evaluation of parenterals:

3.2.1.1. Leaker test:

Leakage occur when a discontinuity exists in the wall of a package that can allow

the passage of gas under the action of a pressure or concentration differential

existing across the wall.

Presence of capillary pores or tiny cracks can cause microbes or other dangerous

contaminants to enter the ampoules or may lead to the leakage of contents to

outside. This may lead to contamination of the sterile contents and also spoilage

of appearance of the package.

Changes in temperature during storage can cause expansion and contraction of

the ampoule and its contents, there by accentuating interchange if an opening

exists.

Leaker test for ampoules is intended to detect incompletely sealed ampoules so

that they can e discarded in order to maintain the sterile conditions of the

medicines.

Tip seal are more likely to be incompletely closed than pull seals.

Open capillaries or cracks at the point of seal result in leakers.

Procedure:

Leakers are detected by this process in a visible manner. Ampoules are placed in

a vacuum chamber. Completely submerged in a deeply colored dye solution of

about 0.5-1% methylene blue.

A negative pressure is applied within the ampoule. Subsequent atmospheric

pressure causes the dye to penetrate on opening thus making it visible after the

ampoule has been washed. The vacuum, about 27 inches Hg, should be sharply

released after 30 minutes.

Detection of leakers is prominent when ampoules are immersed in a bath of dye

during autoclaving cycle as this has the advantage of accomplishing both leaker

detection and sterilization in one operation.

Result: the color from the dye will be visible within a leaker.

Disadvantages:

Capillaries of 15microns or smaller diameter cannot be detected by this test.

Vials and bottles are not subjected to such a leaker test as the rubber closer is

not rigid.

3.2.1.2. Pyrogen test:

i) LAL bacterial endotoxin test:

The LAL (limulus amebocyte lysate) assay is an in vitro assay used to detect the

presence and concentration of bacterial endotoxins in drugs and biological

products.

Endotoxins, which are a type of pyrogen, are lipopolysaccharides present in the

cell walls of gram-negative bacteria.

Pyrogens as a class are fever inducing substances that can be harmfull or even

fatal if administered to humans above certain concentrations. Water can be a

source of pyrogens, so it may be important to routinely monitor water systems

using the bacterial endotoxins test.

Procedure:

The solution of endotoxins containing preparation is added to the lysate derive

from haemolymph cells of horse shoe crab (limulus polyhemus).

The result of the reactions is turbidity or precipitation or gelation of the mixture.

This is used as a quantitative measure to estimate the endotoxin content. The

rate of reaction depends upon concentration of endotoxins, pH, temperature

and presence of clotting enzyme and clottable proteins from lysate.

The quantities of endotoxins are expressed in defined endotoxin units (EU)

The endotoxin limit for a given test preparation is calculated from the expression

k/M; where M is maximum dose administered to adult per kg/hr. The value for K

is 5.0 EU/kg for parenteral preparations and it is 0.2EU/kg for intrathecal

preparations.

Criteria for limulus test result:

LAL TUBE TEST SAMPLE/CONTROL

RESULT

1. Negative control (pyrogen free saline)

Should be -ve

2. Positive control(pyrogen) Should be +ve 3. Positive internal control

(test sample containing exotoxins)

Should be +ve

4. Test sample May be +ve or -ve

Pyrogen test ‘fever response of rabbit’:

SHAM TEST: it is performed to select the proper animals for the main tests.

Rabbit test: qualitative fever response test

The rabbit pyrogen test in an in vivo test to detect pyrogens qualitatively.

Rabbits have a similar pyrogen tolerance to humans, so by observing a change in body

temperature in rabbits it is possible to make a determination of the presence of pyrogens.

This method can detect non-bacterial endotoxin .

Procedure:

Withheld food in the day of experiment.

Record the initial temperature of the rabbits, any rabbit show temperature more than 39⁰c,

should be excluded.

Inject the sample into the ear vein of each rabbit.

Check the temperature after 30 minutes, 1, 2 and 3hrs.

Disadvantages:

Biological variation

Expensive

Laborious

Dose dependent

Not for antipyretic drug

Result:

The test is positive when each rabbit show increase in temperature.

If only two of the three rabbits show increase in temperature, repeat the tes t using

group of five, and test will be positive if the four of the five rabbits show increase in

temperature.

3.2.1.3. Sterility test:

Sterility testing attempts to reveal the presence or absence of viable micro

organisms in a sample number of containers taken from batch of product.

Based on results obtained from testing the sample a decision is made as to the

sterility of the batch.

The primary official test is performed by means of filtration but direct transfer is

used if membrane filtration is unsuitable.

Membrane filtration method:

Media suitable for sterility tests are:

- Fluid thioglycolate medium

- Soya bean casein digest medium

Wash the filters with fluids to remove inhibitory properties, cutting the

membranes aseptically into equal parts and transferring one of the parts to each

type of culture medium used.

The media are then incubated under prescribed conditions.

Direct inoculation method:

This method is only used when membrane filtration is not possible the sample is

inoculated directly into the media or the device is placed directly into the media.

Result: If no growth in the media then test is positive.

3.2.1.4. Particulate evaluation:

- It has been shown that particles of lint, rubber, insoluble chemicals and other

foreign matter can produce emboli in the vital organs of animals and human

beings.

- The USP specifies that good manufacturing practice(GMP) requires that each

final container of an injection be subjected individually to a visual inspection and

that containers in which visible particles can be seen should be discarded.

- Therefore, all of the product units from a production line currently are being

inspected individually by human inspectors under a good light, baffled against

reflection into the eye and against a black-and-white back ground.

- The USP has identified two test methods.

- The first test to be used is the light obscuration test, which uses and electronic

instrument designed to count and measure the size of the particles by means of a

shadow cast by the particle as it passes through a high-intensity light beam.

- If the injection formulation is not a clear, colorless solution, it exceeds the limits

specified for the light obscuration test, it is to be subjected to the microscopic

count test.

3.2.1.5. Weight variation or uniformity of content:

- This test is intended for sterile solids used for parenteral preparations.

- The weight of 10 individual sterile units is notes and the content is removed

from them and empty individual sterile unit is weighed inturn.

- Then content of active ingredient in each sterile unit is calculated by

subtracting empty sterile unit is calculated by performing the assay according

to the individual monographs.

- Then net weight is calculated by subtracting empty sterile unit weight form

gross weight.

- The content in 10 sterile units is calculated by performing the assay.

- The dose uniformity is met if the amount of active ingredient is within the

range of 35-115% of label claim as determine by the content uniformity

method or weight variation method.

- The dose uniformity is also met if the potency value is 100% in the individual

monograph or less of label claim multiplied by average of limits specified for

potency in individual monograph divided by 100 provided that the relative

standard deviation in both the cases is equal to or less than 60%. The fore

mentioned test is carried for 20 more sterile units14.

- The sterile units meet the requirements if not more than one unit is outside

the range of 85-115%, no unit is outside the range of 75-125% and the

calculated

Relative standard is NMT 7.8%.

3.2.2. EVALUATION OF EYE DROPS

Following tests are carried out for the evaluation of eye drops:

3.2.2.1. Test for sterility

All the ophthalmic preparations should be sterile i.e., free from any viable organism

and its spores. Ophthalmic preparations are tested for their sterility.

The following criteria should be followed while carrying out sterility testing. Two

sterile culture media are prepared for the detection of aerobic and anaerobic bacteria and

fungi.

Table: culture media in test for sterility

Medium Micro organism

1. Fluid thioglycollate medium Detects the presence of aerobic and

anaerobic bacteria.

2. Soybean casein digest medium. Detects the presence of fungi and aerobic

bacteria.

Test samples are transferred into test tubes containing clear medium. If the sample contains

microorganisms, then the medium becomes turbid. If the sample is free from

microorganisms, then the medium remains clear. The tests should be carried out in aseptic

conditions.

Procedure:

a. Membrane filtration method/method A

This method is generally followed for the products which can be easily filtered and is carried

out in aseptic conditions.

The apparatus consists of a sterilized filter unit with sterile membrane filter of 0.45 µ pore

size. A single membrane filter is divided into two equal halves. The test solution is filtered

through the membrane filer. One half of the membrane is placed in fluid thioglycollate

medium at 30-35°C and other half is placed in soybean casein digest medium at 20-25°c for

7 days.

Result: If the medium shows no growth, then the sample solution passes the test. If the

medium shows growth, then the test is repeated. If the growth is observed again, then the

sample solution fails the test.

b. Direct inoculation method/method B

Specified quantity of the solution to be tested is drawn through a sterile syringe or pipette.

It is mixed with the medium and incubated for 14 days at a specific temperature. Between

3rd and 7th day of incubation, a portion of medium is transferred to a fresh medium, if it

shows turbidity, then both the old and fresh media are incubated for 14 days.

Result: If the medium shows no growth, then the sample solution passes the test. If the

medium shows growth, then the test is repeated. If growth is observed again, then the

sample fails the test.

3.2.2.2. Test for ocular toxicity and irritation

This test assesses the isotonicity of the preparation.

Procedure:

Five albino rabbits are selected, the iridal vessels of whom can be easily observed for

toxicity and irritation. Based on the type of dosage form, the medicament is extracted using

cotton seed oil or saline. Small quantities of the extract are instilled into one eye of all the

rabbits, while sterile saline solution is instilled into the other eye. After one hour all the

rabbits are observed for irritation, swelling or shrinkage of the eye.

Result: No change in the eye into which the preparation is instilled indicates that the

preparation under test is safe for use.

3.2.2.3. Test for preservative efficacy

a. Cultures of microorganisms like Aspergillusniger, Candida albicans, Escherchia coli and

Pseudomonas aeruginosa, each containing about 10,000 – 10,00,000 organisms per ml are

selected.

b. Three to four samples of each preparation are taken in sterile test tubes and inoculated

with few ml of each culture separately.

c. They are incubated at 20 - 25°C for a period of 28 days and are observed weekly for the

appearance of turbidity.

d. No growth of microorganisms indicates that the preservative is totally effective.

3.2.2.4. Clarity

The clarity of the formulations before and after gelling was determined by visual

examination of the formulations under light alternatively against white and black

backgrounds.

3.2.2.5. pH

The pH of each of prepared ophthalmic formulations was determined by using pH meter

(equip-tronics). The pH meter was calibrated before each use with standard pH 4, 7 and 9.2

buffer solutions.

3.2.2.6. In vitro diffusion studies

In vitro release studies were carried out using bi chambered donor receiver compartment

mode (Franz diffusion cell). In vitro release was carried out in formulations with different

concentrations of gelrite using dialysis membrane. The diffusion medium 26ml of simulated

tear fluid stirred at 50 rpm at 370 C ±0.50 C. One end of the diffusion tube was covered by a

dialysis membrane. The1 ml formulation were spread on the dialysis membrane and

membrane was placed such that it just touches the diffusion medium (STF) present in

receptor compartment. The drug samples were withdrawn at the interval of one hour for

the period of 8 hrs from diffusion medium and analyzed by a UV spectrophotometer at 261

nm using simulated tear fluid as blank.

3.2.2.7. Determination of viscosity

The specified volume of prepared ophthalmic solution was transferred in sample cell which

was placed carefully within the adaptor (Brookfield DV-II + PRO viscometer, Adapter spindle

No-18).The water of 25°C was circulated through jacket of the adaptor. The viscosity values

were recorded.

4. EVALUATION TESTS FOR AEROSOLS

Following tests are carried out for the evaluation of aerosols:

4.1. Flammability and combustibility:

4.1.1. Flash point:

Apparatus : open cup tag apparatus.

Test liquids temperature is allowed to increase slowly and temperature of which vapors

ignite is called is called as flash point.

Standard tag open cap

apparatus

4.1.2. Flame projection:

Product is sprayed for 4 seconds onto flame and exact length is measured with ruler.

4.2. Physicochemical characteristics:

Property Method

Vapor pressure Can puncturing device

Density Hydrometer

pycnometer

Moisture Karl fischer method

Gas chromatography

Identification Gas chromatography

IR spectroscopy

4.3. Performance:

4.3.1. Aerosol valve discharge rate:

Aerosol product of known weight is discharged for specific time. By reweighing the

container, the change in the weight per time dispensed is the discharge rate in gm/sec.

4.3.2. Spray pattern:

This method is based on the impingement of spray on piece of paper that has treated with

Dye-Talc mixture.

4.3.3. Dosage with metered valves:

Reproducibility of dosage determined by:

Assay :

Accurate weighing of filled containers followed by dispensing several dosages. Containers

again reweighed and differ in weight divided by number of dosage dispensed gives average

dose.

4.3.4. Net contents:

Tared cans placed on filling lines are reweighed and then difference in weight is equal to net

content.

In destructive method: Opening the container and removing as much of product possible.

4.3.5. Foam stability:

Various methods are there namely,

Visual evaluation

Time for given mass to penetrate the foam

Time for given rod to fall which is inserted into the foam

Rotational viscometer.

4.3.6. Particle size determination:

Methods :cascade impactor, light scattering decay.

Cascade impactor:

Principle: Stream of particle projected through a series of nozzle and glass slide and at high

velocity. Larger particles are impacted on low velocity stage and smaller on higher velocity

stage.

Light scattering decay:

Principle: As aerosol settles under turbulent condition, the changes in the light of a tyndall

beam is measured.

4.4. Biological testing:

Therapeutic activity:

For inhalation aerosols – is depends on the particle size.

For topical aerosols - is applied to test areas and adsorption of therapeutic ingredient is

determined.

Toxicity:

For inhalation aerosols: Exposing test animals to vapor sprayed from aerosol container.

For topical aerosols: Irritation and chilling effects are determined15.

5. EVALUATION OF NASAL SPRAY

Following are tests carried out for the evaluation of nasal spray:

5.1. Appearance, Colour, and Clarity:

The appearance of the content of the container (i.e., formulation) and the container closure

system (e.g., pump components, inside of the container) should confirm totheir respective

descriptions as an indication of the drug product integrity. If any colour is associated with

the formulation (either present initially or from degradative processes occurring during shelf

life) then a quantitative test with appropriate acceptance criteria should be established for

the drug product by the manufacturer.

5.2. Drug Content (Assay):

The assay of drug substance in the entire container should be determined analytically with a

stability indicating procedure. This test provides assurance of consistent manufacturing

(e.g., formulation, filling, sealing). The acceptance criteria (assay limits as specified in official

books) should be tight enough to ensure conformance in other related attributes (e.g., spray

content uniformity). A suitable assay procedure should be designed to address any

degradation of the drug substance, adherence of the drug substance to the container and

closure components, and the potential effect of formulation evaporation and/or leakage.

5.3. Impurities and Degradation Products:

The levels of degradation products and impurities should be determined by means of

stability indicating procedure(s). Acceptance criteria should be set for individual and total

degradation products and impurities. For identification and qualification thresholds, refer to

the appropriate guidance. All related impurities appearing at levels of 0.1 percent or greater

should be specified. Specified impurities and degradation products are those, either

identified or unidentified, that are individually listed and limited in the drug product

specification.

5.4. Preservative(s) and Stabilizing Excipient(s) Assay:

If preservatives, antioxidants, chelating agents, or other stabilizing excipients (e.g.,

benzalkonium chloride, phenylethyl alcohol, edetate) are used in the formulation, there

should be a specific assay for these components with associated acceptance criteria (At a

concentration of 0.10 percent or 1.0 milligram per day).

5.5. Pump Delivery:

A test to assess pump-to-pump reproducibility in terms of drug product performance and to

evaluate the metering ability of the pump should be performed. The proper performance of

the pump should be ensured primarily by the pump manufacturer, who should assemble the

pump with parts of precise dimensions. Pump spray weight delivery should be verified by

the applicant for the drug product. In general, pump spray weight delivery acceptance

criteria should control the weight of the individual sprays to within ±15 percent of the target

weight and their mean weight to within ±10 percent of the target weight.

5.6. Spray Content Uniformity (SCU):

The spray discharged from the nosepiece should be thoroughly analyzed for the drug

substance content of multiple sprays from an individual container, among containers, and

among batches of drug product. This test should provide an overall performance evaluation

of a batch, assessing the formulation, the manufacturing process, and the pump. The

number of sprays per determination should not exceed the number of sprays per single

dose. A single dose represents the minimum number of sprays per nostril specified in the

product labelling. To ensure reproducible in vitro dose collection, the procedure should

have controls for actuation parameters (e.g., stroke length, depression force). The test may

be performed with units primed following the instructions in the labelling. The amount of

drug substance delivered from the nosepiece should be expressed both as the actual

amount and as a percent of label claim. This test is designed to demonstrate the uniformity

of medication per spray (or minimum dose), consistent with the label claim, discharged from

the nosepiece, of an appropriate number (n = 10 is recommended) of containers from a

batch. The primary purpose is to ensure SCU within the same container and among multiple

containers of a batch. The following acceptance criteria are recommended:

The amount of active ingredient per determination is not outside of 80–120 percent of label

claim for more than 1 of 10 containers, none of the determinations is outside of 75–125

percent of the label claim, and the mean is not outside of 85–115 percent of label claim.

If 2 or 3 of the 10 determinations are outside of 80–120 percent of the label claim, none is

outside of 75–125 percent of label claim, and the mean is not outside of 85–115 percent of

label claim, an additional 20 container should be sampled (second tier). For the second tier

of testing of a batch, the amount of active ingredient per determination is not outside of

80–120 percent of the label claim for more than 3 of all 30 determinations, none of the 30

determinations is outside of 75–125 percent of label claim, and the mean is within 85–115

percent of label claim.

5.7. Spray Content Uniformity (SCU) through container life:

The purpose of this test is to assess whether the product delivers the labelled number of full

medication sprays meeting SCU acceptance criteria throughout the life of the nasal spray

unit. The test involves determining the SCU from the beginning of unit life and at the label

claim number of sprays per container for an appropriate number of containers (n = 5 is

recommended). The following acceptance criteria are recommended.

The amount of active ingredient per determination is not outside of 80–120 percent of label

claim for more than 1 of 10 determinations from five containers, none of the

determinations is outside of 75–125 percent of the label claim, and the means for each of

the beginning and end determinations are not outside of 85–115 percent of label claim.

If 2 or 3 of the 10 determinations are outside of 80–120 percent of the label claim, none is

outside of 75–125 percent of label claim, and the means for each of the beginning and end

determinations are not outside of 85–115 percent of label claim, an additional 10 containers

are sampled at the beginning of unit life and at the label claim number of sprays (second

tier). For the second tier of testing of a batch, the amount of active ingredient per

determination is not outside of 80–120 percent of the label claim for more than 3 of all 30

determinations, none of the 30 determinations is outside of 75–125 percent of label claim,

and the means for each of the beginning and end determinations are not outside of 85–115

percent of label claim.

5.8. Droplet Size Distribution:

For both suspension and solution nasal sprays, the specifications should include an

appropriate control for the droplet size distribution (e.g., 3 to 4 cut-off values) of the

delivered plume subsequent to spraying under specified experimental and instrumental

conditions. Appropriate and validated dynamic plume droplet size analytical procedures

should be described in sufficient detail to allow accurate assessment by Agency laboratories

(e.g., apparatus and accessories, software version and calculation algorithms, sample

placement, laser trigger condition, measurement range, beam width).

5.9. Foreign Particulates:

For both solution and suspension nasal sprays, there should be validated tests and

associated acceptance criteria for foreign particulates. Foreign particulates may originate

during manufacturing, from formulation components, and, in particular, from the container

and closure components. Levels of foreign particulates in the drug product may increase

with time, temperature, and stress.

5.10. Microbial Limits:

The microbial quality should be controlled by appropriate tests and acceptance criteria for

total aerobic count, total yeast and mold count, and freedom from designated indicator

pathogens. Acceptance criteria should be reflective of the data for the submitted batches

(e.g., clinical, preclinical, biobatch, primary stability, production), but at a minimum should

meet the recommended microbial limits acceptance criteria in USP <1111>, Microbiological

Attributes for Non-sterile Pharmacopoeial Articles. Furthermore, appropriate testing should

show that the drug product does not support the growth of microorganisms and that

microbiological quality is maintained throughout the expiration dating period. For a

description of this test, refer to the procedure in USP <61>.

5.11. Preservative Effectiveness:

For nasal sprays that contain a preservative(s), stability testing should include microbial

challenge studies performed on the first three production batches of drug product.

5.12. Net Content and Weight Loss (Stability):

Nasal spray drug products should include acceptance criteria for net content and weight loss

on stability. Since storage orientation plays a key role in any weight loss, the drug product

should be stored in upright and inverted or upright and horizontal positions to assess this

characteristic.

The total net content of all formulation components in the entire container should be

determined. The net content ofeach of 10 test containers should be in accordance with the

release specification. For a description of this test, refer to the procedure in USP Chapter

<755> Minimum Fill.

5.13. Leakage testing:

The drug product should be evaluated for compounds that leach from elastomeric or plastic

components of the container closure system, such as nitrosamines, monomers , plasticizers,

accelerators, antioxidants, and vulcanizing agents. The development of appropriate

analytical procedures to identify, monitor, and quantify the leached components in the drug

product should be done during investigational studies. These validated procedures can, in

turn, be used for testing of the drug product throughout the expiration dating period.

Appropriate acceptance criteria for the levels of leached compounds in the formulation

should be established.

5.14. pH:

For both solution and suspension nasal sprays, the apparent pH of the formulation should

be tested and an appropriate acceptance criterion established. Lysozyme is found in nasal

secretions, which is responsible for destroying certain bacteria at acidic pH. Under alkaline

conditions, lysozyme is inactivated and the nasal tissue is susceptible to microbial infection.

It is therefore advisable to keep the formulation at a pH of 4.5 to 6.5 keeping in mind

thephysicochemical properties of the drug as drugs are absorbed in the un-ionized form.

5.15. Osmolality:

The osmolality of the formulation should be tested and controlled with an appropriate

procedure and acceptance developed by manufacturer16.

6. COSMETICS:

6.1. EVALUATION OF LIPSTICKS:

Following are the tests carried out for the evaluation of lipsticks:

6.1.1. Surface anomalies:

This is studied by the surface defects such as formation of crystals on surface,

contamination by moulds and fungi etc.

6.1.2. Thixotropic characters:

This is an indication of thixotropic quality and is done by using penetromete r. A standard

needle of specific diameter is allowed to penetrate for 5 seconds under 50gms load at

room temperature. Penetration of the needle upto 9-10.5 mm is indicative of soft and

thixotropic structure.

6.1.3. Breaking point:

This test is done to determine the strength of lipsticks. The lipstick is held horizontally

and weights are applied on the lipstick and increase the weights at a specific time

interval of 30 seconds. The weight at which the lipstick breaks is considered as breaking

point.

6.1.4. Melting point:

This is carried out by using capillary tube method.

7. NOVEL DRUG DELIVERY SYSTEMS:

7.1. EVALUATION OF TRANSDERMAL PATCHES

Development of controlled release transdermal dosage form is a complex process involving

extensive research. Transdermal patches have been developed to improve clinical efficacy

of the drug and to enhance patient compliance by delivering smaller amount of drug at a

predetermined rate. This makes evaluation studies even more important in order to ensure

their desired performance and reproducibility under the specified environment conditions.

These studies are predictive of transdermal dosage forms and can be classified into

following types:

I. Physicochemical evaluation

II. In vitro evaluation

III. In vivo

Physicochemical evaluation:

7.1.1. Thickness:

The thickness of transdermal film is determined by travelling microscope, dial gauge,

screw gauge or micrometer at different points of the film.

7.1.2. Uniformity of weight:

Weight variation is studied by individually weighing 10 randomly selected patches

and calculating the average weight. The individually weight should not deviate significantly

from the average weight.

7.1.3. Drug content determination:

An accurately weighed portion of film (about 100 mg) is dissolved in 100 ml of

suitable solvent in which drug is soluble and then the solution is shaken continuously for

24hrs in shaker incubator, then drug in solution is estimated spectrophotometrically by

appropriate dilutions.

7.1.4. Content uniformity test:

10 patches are selected and content is determined for individual patches. If ali

quotes of 10 patches have content between 85% to 115% of the specified value and one has

content NLT 75% to 125% of the specified value, then transdermal patches pass the test of

content uniformity. But if 3 patches have content in the range of 75% to 125%, then

additional 20 patches have range from 85% to 115% then the transdermal patches pass the

test.

7.1.5. Moisture content:

The prepared films are weighed individually and kept in a desiccators containing

calcium chloride of room temperature for 24 hrs. The films are weighed again after a

specified interval until they show a constant weight. The % moisture content is calculated

using following formula.

%moisture content = initial weight – final weight × 100/ final weight

7.1.6.Moisture uptake:

Weighed films are kept in desiccators at room temperature for 24hrs. These

are then taken out and exposed to 84% relative humidity using saturated solution of

potassium chloride in desiccators until a constant weight is achieved. % moisture uptake is

calculated as given below.

% moisture uptake = final weight – initial weight × 100/ final weight

7.1.7.Flatness:

A transdermal patch should possess a smooth surface and should not

constrict with time. This can be demonstrated with flatness study. For flatness

determination, one strip is cut from the centre and two from each side of patches. The

length of each strip is measured and variation in length is measured by determining percent

constriction. Zero percent constriction is equivalent to 100% flatness.

% constriction = I1 – I1/ I1 × 100

I2 = final length of each strip

I1= initial length of each strip

Folding endurance:

Evaluation of folding endurance involves determining the folding capacity of

the films subjected to frequent extreme conditions of folding. Folding endurance is

determined by repeatedly folding the films at the sample place until it break. The number of

times the films could be folded at the same place without breaking is folding endurance

value.

7.1.8. Tensile strength:

To determine tensile strength, polymeric films are sandwiched separately by corked linear

iron plates. One end of the films is kept fixed with the help of an iron screen and other end

is connected to a freely movable thread over a pulley. The weights are added gradually to

the pan attached with the hanging end of the thread. A pointer on the thread is used to

measure the elongation of the film. The weight just sufficient to break the film is notes. The

tensile strength can be calculated using the following equation.

Tensile strength = F/a.b(l+L/l)

F is the forced required to break;

a is width of film

b is the thickness of film

L is length of film

l is elongation of film at break point.

7.1.9. Peel adhesion properties:

It is the force required to remove adhesive coating from test substrate. It is

tested by measuring the force required to pull a single coated tape, applied to substrate at

180⁰ angle. The test is passed of there is no residue on the substrate.

7.1.10.Tack properties:

It is the ability of the polymer to adhere to substrate with little contact

pressure. Tack is dependent on molecular weight and composition of polymer as well as on

the use of tackifying resins in polymer.

7.1.11. Thumb tack test:

The force required to remove thumb from adhesive is a measure of tack.

7.1.12. Rolling ball test:

This test involves measurement of the distance that stainless steel ball travels

along an upward facing adhesive. The less tacky the adhesive, the further the ball will travel.

7.1.13. Quick- stick (peel tack):

The peel force required breaking the bond between an adhesive and

substrate is measured by pulling the tape away from the substrate at 90⁰at the speed of

12inch/min.

7.1.14. Probe tack test:

Force required to pull a probe away from an adhesive at a fixed rate is

recorded as tack.

7.1.15. Shear strength properties (or) creep resistance:

Shear strength is the measurement of the cohesive strength of an adhesive

polymer i.e., device should not slip on application determined by measuring the time it

takes to pull an adhesive coated tape off a stainless plate17.

REFERENCES:

1. http://www.authorstream.com/Presentation/narmdeshwar25-1194326-tablet-evaluation/

http://apps.who.int/phint/en/p/docf/

2. Abolfazl Aslani* "Formulation, Characterization and Physicochemical Evaluation of

Ranitidine Effervescent Tablets" Adv Pharm Bull. 2013 Dec; 3(2): 315–322.

3. P.Chinna Reddy* " A review on bioadhesive buccal drug delivery systems: current status of

formulation and evaluation methods" Daru. 2011; 19(6): 385–403.

4. Jaysukh J Hirani "Orally Disintegrating Tablets: A Review"Tropical Journal of

Pharmaceutical Research, April 2009; 8 (2): 161-172

5. SANTOSH GIRI, SELLAPPAN VELMURUGAN*" FORMULATION AND EVALUATION OF GLIPIZIDE SUSTAIN RELEASE MATRIX TABLETS" International Journal of Pharmacy and Pharmaceutical Sciences, Vol 5, Suppl 1, 2013 .

6. http://www.slideshare.net/ammu909/seminar-on-manufacturing-and-evaluation-of-capsules?qid=50bcc48e-5203-48ab-a3f2-4f675ea6d407&v=default&b=&from_search=1

7. http://www.slideshare.net/divyanaidu733/divya-35153858?qid=5c860750-2928-4e96-

b8fd-b4b8c3bc9ad2&v=default&b=&from_search=2

8. http://www.pharmainfo.net/evaluation-ointments

9. http://www.slideshare.net/VIJAYSINGH158/evaluation-ofsemisoliddosageforms?qid=02d672e8-

4d5e-48a7-b2bd-fb7a6a25677c&v=qf1&b=&from_search=3

10. M.A.Saleem* "Formulation and Evaluation of Tramadol hydrochloride Rectal

Suppositories" Indian J Pharm Sci. 2008 Sep-Oct; 70(5): 640–644.

11. http://www.slideshare.net/bhatti106/quality-control-tests-for-syrups-and-elixirs

12. .Indian pharmacopoeia 2014, 7th edition

13.Indian pharmacopoeia 2014, 7th edition

14. http://www.slideshare.net/anniechocolateprincess/quality-control-of-parenteral-preparations?qid=21d31897-8dd0-4320-ad04-40f38d17179c&v=default&b=&from_search=5

15. The theory and practice of industrial pharmacy by Leon lachman, Herbert A lieberman,

fourth edition.

16. http://journals.indexcopernicus.com/issue.php?id=11066&id_issue=860703

17. www.arpb.info/Pharma/admin1/user/download/7812ARPB-2116.pdf