Routes of drug administration

ROUTES OF DRUG ADMINISTRATION

Presented by:Yusuf Nawaz KhanRY1507A06

• May be classified as• Enteral • Parenteral.

• Enteral means through the GI tract and includes oral, buccal, and rectal. • Parenteral means not through GI and commonly

refers to injections such as IV, IM, and SC; but could also include topical and inhalation. • They have to cross at least one membrane

before reaching the systemic circulation (except in IV).

Introduction

Buccal/Sublingual Administration

• Drug is taken as smaller tablets which are held between cheek and gum or under the tongue.• Buccal tablets are often harder tablets, designed

to dissolve slowly ; on the other hand sublingual tablets are having less hardness to show fast action. • Main barrier is epithelial of oral mucosa.• This ROA is also used for some steroids such as

testosterone and oxytocin; other than that we are using antianginal drugs.• Mainly passive diffusion is major mechanism of

absorption.• Nutrients can follow carrier mediated process.

Advantage and disadvantage• Advantages –

i. Rapid absorption due to high vasculature.ii. No first pass hepatic metabolism.iii. No degradation due to neutral pH of saliva.

• Disadvantages – Only small dose can be given due to limited mucosal surface area.

Factors affecting absorptioni. Lipophilicity of the drug: • Slightly higher lipid solubility required than for GI absorption.

ii. Salivary secretion:• Drug must be soluble in aqueous buccal fluid.• Absorption is delayed if mouth is dry.

iii. pH of the saliva:─ Favorable absorption rate for drug unionised at pH 6.

iv. Binding to oral mucosa:• Binding decreases bioavailability.

v. Thickness of oral epithelium:• Sublingual faster than buccal.

Topical Administration Drug can diffuse by-• Intracellular (passive diffusion)• Intercellular (paracellular)• Transappendageal –

i. Hair follicles.ii. Sweat glands.iii. Sebaceous glands.

Main barrier is stratum corneum.

Factors affecting absorption• Thickness of stratum corneum- absorption is slow in foot and

more in palm.• Presence of hair follicles – more in follicles regions.• Trauma- increase absorption.• Hydration – promotes absorption.• Age – infants absorbs more than adults.• Ionized and soluble drug absorbs more.• Permeation enhancer increase absorption.• Exposer to chemical enhance absorption by shedding off of

stratum corneum.• Chronic use of keratolytic enhance penetration.

Rectal Administration• Most commonly used for suppository or enema. • Some drugs given by this route include: • Aspirin, theophylline, paracetamol and barbiturates.

• Advantages: • By-pass liver - Some of the veins draining the rectum lead

directly to general circulation - by-passing the liver. • Useful for patients unable to take drugs orally or with younger

children. • Disadvantages: • Presence of fecal matter retards absorption.• Slow absorption due to limited surface area. • Not well accepted.

Intravenous Administration

• The drug is injected as a bolus or infused slowly over hours in one of the superficial veins.• The drug reaches directly into the blood stream• Rapid injections are used to treat epileptic seizures,

acute asthma, or cardiac arrhythmias etc.• No absorption barrier is there.• Quick response is possible.• Large dose can be given by infusion.• Require trained personnel.• Expensive and chances of toxicity or infection.

Intramuscular Administration• Absorption is rapid but in comparison to i.v. it is slower.

Factors affecting absorption

i. Vascularity at injection site – (deltoid)>(vastus lateralis)>(gluteus maximus)ii. Lipid solubility and ionisation – highly lipid soluble drug are

more absorbed quickly and hydrophilic/ionised drug are slowly absorbed by capillary pores.

iii. Molecular size – small molecules and ion go to capillary through pores and larger go to lymphatic system.

iv. Volume and drug conc – Conc and high volume absorbed rapidly.

v. pH and viscosity – drug solution in acidic/basic or nonaqueous solvent result in slow release.

Subcutaneous Administration• This involves administration of the drug dose just under the skin. • Absorption is slower in comparison to i.m.• Important when rapid response is not required or drug degrade

when taken orally (insulin).• Increasing the rate of absorption –

i. Enhancing blood flow – massage, applying heat, vasodilators, exercise.

ii. Increasing drug-tissue contact time – administering enzyme hyaluronidase.

• Decreasing the rate of absorption – Cooling , vasoconstrictors, immobilization of limb.

• Mainly use controlled release medication.

Pulmonary Administration• In principle we can use all systemic effective drug can be

administered.• Only use for bronchodilator, anti-inflammatory steroids,

anesthetics and anti-allergic.• Lipid soluble drug absorbed by passive diffusion.• Polar drug by pore transport.

Nasal Administration• Utilized only for local effects.

• For drugs that are destroyed in the GI environment (or first-pass effect).

• As an alternative to intravenous administration• Better safety and patient acceptance

Mechanism of drug transport-i. Faster rate depend upon lipophilicity.ii. Slower rate depend upon molecular weight.

Intraocular Administration

• Preparation should be sterile aqueous.• Barrier is cornea (lipophilic + hydrophilic).• Higher pH decrease tear flow and lower pH increase

lachrymation/decrease absorption. • Small concentrated solution is more effective than large

volume/less concentrated.• Oily or viscous solution are more effective.

Vaginal Administration Drug intended to act locally-i. In treatment of bacterial or fungal infection.ii. To prevent conception.

• No first pass metabolism.• Controlled delivery and termination of action when desired is

possible.

• Biopharmaceutics And Pharmacokinetics- A Treatise By D.M.Brahmankar And Sunil B. Jaiswal.

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