LIQUID DOSAGE FORMS - Centurion University

LIQUID DOSAGE FORMS

By

C.Nivetha

IV Pharm. D

INTRODUCTION:

• A liquid dosage form is the liquid form of a dose

of a chemical compound used as a drug or

medication intended for administration or

consumption.

• Monophasic liquid dosage forms are

represented by true or colloidal solution.

• The component of the solution which is

present in a large quantity is know as

“SOLVENT” where as the component present

in small quantity is termed as “SOLUTE”.

Classification:

Monophasic liquid dosage form:

A.INTERNAL:

1. Mixture

2. Syrup

3. Elixir

4. Linctus

B. EXTERNAL:

1. Application on the skin: liniment, lotion

2. Used in the mouth: gargles , mouth wash , throat paint

3. Instilled into body cavities : douche , ear drop , nasal drop, nasal spray

Liquids meant for internal

administration: MIXTURES:

A mixture is a liquid preparation meant for oral administration in which medicament or medicaments are dissolved or suspended in a suitable vehicle

Mixtures are not prepared to keep them for a long period because they are mainly prescribed for acute condition such as cough, indigestion ,diarrhoea,constipation.

Classification:

Simple mixtures containing soluble

substances.

Mixtures containing diffusible solids.

Mixtures containing indiffusible solids.

Mixtures containing precipitates forming

liquids.

Mixtures containing slightly soluble

liquids.

Formulation of mixtures:

1.Vehicles:The vehicle commonly used for

the preparation of mixtures are:

(a) Water : Purified water should be used

for the preparation of mixtures.

(b) Aromatic water : These are saturated

solution of volatile oil and volatile

substance in purified water. Aromatic

water is mainly used for its flavouring

properties.

cont….

2.Adjuncts:

a) Chemical stabilizers : Certain chemicals

having antioxidants or reducing

properties are used to improve the

chemical stability of the mixtures.

Eg . ascorbic acid, sodium metabisulphite

b) Colouring agents: No special colouring

agents are added but many mixture

contain coloured medication

cont….

(c) Flavouring agents: The following flavouring agents are added commonly used in mixtures:

Aromatic water such as anise water.

Syrup and glycerol for sweetening children preparation

Liquid extract of liquorice to mask the saline taste.

Spirit lemon to cover the taste of alkaline citrates

cont….

(d) Preservative: Diluted vegetables extract

and flavouring agents are the source of

growth of micro organism. Hence

chloroform(0.25%) and benzoic

acid(0.1%) is used to preserve such

mixture.

SYRUPS: A syrup is a concentrated solution of sucrose in

purified water.

The concentration of sugar is 66.7% w/w.

Formulation of syrup:

Vehicle: purified water

Chemical stabilizers : glycerin , sorbitol , propylene glycol

Colouring agents : coal tar dyes such as amaranth is used.

Flavouring agents : tinctures lemon , fruit juices , essence.

Preservatives: the syrup containing 66.7% w/w of sucrose have high osmotic pressure which prevents growth of microorganism. So no preservative is needed.

Preparation of syrup:

water + sucrose(heating)

stir well

filter

allow it to cool

cont….

API + add q.s.water to solubilize

other agents

then mix with simple syrup

Sucrose should not dissolved in high temperature because the sucrose gets hydrolysed, results in the formation of dextrose and fructose, these two sugars together called as invert sugar and the process is known as inversion. This reaction takes place more rapidly in presence of acids. The inversion leads to darkening of the solution.

SOLUTION

Solutions are clear Liquid preparations

containing one or more active ingredients

dissolved in a suitable vehicle.

CLASSIFICATION OF SOLUTION:

a) Oral solutions—through oral route.

b) Otic solutions—instilled in the ears.

c) Ophthalmic solution—instilled in the eyes.

d) Topical solutions—applied over the skin

surface.

METHODS OF PREPARATION

Methods of Preparation of Solutions

(a) Simple Solution

(b) Solution by Chemical Reaction

(c) Solution by Extraction

Simple solution:

Simple Solution Solutions of this type are

prepared by dissolving the solute in a

suitable solvent (by stirring or heating ).

The solvent may contain other

ingredients which stabilize or solubilize

the active ingredient .

E.g. solubility of iodine is more in KI when

compared with water because the

formation of soluble polyiodides

Solution by chemical reaction:

These solutions are prepared by reacting two or more solutes with each other in a suitable solvent e.g. Calcium carbonate and lactic acid used to prepare Calcium lactate mixture.

Solution by Extraction:

• Solution by Extraction Plant or animal products are prepared by suitable extraction process. Preparations of this type may be classified as solutions but more often, are classified as extractives.

BIPHASIC LIQUID DOSAGE

FORM 2 types of biphasic liquid dosage form are:

(i) Suspension

(ii) Emulsion

SUSPENSION

Suspension are the biphasic liquid dosage form of medicaments in which the finely divided solid particles ranging from 0.5 to 5.0 microns are dispersed in a liquid or semisolid vehicle.

The solid particles act as disperse phase whereas liquid vehicle act as the continuous phase

The particle size of the disperse phase is very important in the formulation of suspensions.

Qualities of suspension:

It should settle slowly and should be readily re-dispersed on gentle shaking of the container.

The suspension should pour readily and evenly from its container.

It should be chemically inert.

The suspended particles should not form a cake.

It should be free from large particles which spoil its appearance.

Classification of suspension

Oral suspension

Parenteral suspension

Ophthalmic suspension

Suspension of external use

Flocculated and Non-flocculated

suspension: The suspension are said to be flocculated

, when the individual particles are in

contact with each other and form a

network like structure.

Whereas in case of non-flocculated

suspension , the individual particles exists

as a separate entity.

Components

Function

API Active

drug substances

Wetting

agents

They

are added to disperse solids in continuous liquid phase.

Flocculating

agents

They

are added to floc the drug particles

Thickeners They

are added to increase the viscosity of suspension.

Buffers

and pH adjusting agents

They

are added to stabilize the suspension to a desired pH range.

Osmotic

agents

They

are added to adjust osmotic pressure comparable to biological

fluid.

Coloring

agents

They are added to impart desired color to suspension and

improve elegance.

Preservatives They

are added to prevent microbial growth.

External

liquid vehicle

They are added to construct structure of the final suspension.

Preparation of suspension:

EMULSION

An emulsion is a thermodynamically unstable system consisting of at least two immiscible liquid phases one of which is dispersed (the dispersed phase) as globules in the other liquid phase (the continuous phase) stabilized by a third substance called emulsifying agent.

Particle diameter of dispersed phase (Internal phase) ranged from 0.1 to 10 µm.

TYPES OF EMULSION

Oil-in-water (O/W)

Water-in-oil (W/O)

DIFFERENCE BETWEEN O/W

AND W/O EMULSIONS:

O/W EMOLSION W/O EMULSION

Water is the dispersion medium

and oil is the dispersed phase

Oil is the dispersion medium and

water is the dispersed phase

non greasy and easily removable

from the skin

greasy and not water washable

used externally to provide cooling

effect e.g. vanishing cream

used externally to prevent

evaporation of moisture from the

surface of skin e.g. Cold cream

preferred for internal use as bitter

taste of oils can be masked.

preferred for external use like

creams.

Formulation of emulsion

(A) Emulsifying agent:

The emulsifying agent reduces the

interfacial tension between two phases

i.e.oily phase and aqueous phase and

thus make them miscible with each

other and form stable emulsion.

IDEAL PROPERTIES OF

EMULSIFYING AGENT: It should be capable of reducing the

interfacial tension between the two immiscible liquids

It should be compatible with other ingredients of the preparation

It should be non toxic

It should be capable to produce and maintain the required consistency of the emulsion

It should be chemically stable

Classification of emulsifying agent:

(i)Natural

(a)From plant origin

Polysaccharides ( Acacia, tragacanth, agar, pectin)

(b)From animal origin

Proteins ( Gelatin)

Lecithin

Cholesterol

Wool fat

Egg yolk

(ii)Semi synthetic ( Multi molecular films)

Methyl cellulose

Carboxy methyl cellulose

Preparation of emulsion:

Water in oil type emulsion:

internal phase(water)+emulsifying agent

triturate well

add external phase(oil) in drop wise

(primary emulsion)

Triturate until a homogenous phase is formed

Oil in water type emulsion: visa versa