Routes Of Administration

Question 1

Definition of bioavailability

Answer 1

The fraction of administered drug that reaches the systemic circulation in an unchanged form

Question 2

Bioequivalance

Answer 2

Two related drugs:

• show comparable bioavailability
• similar times to achieve peak blood concentrations

Question 3

Therapeutic equivalance

Answer 3

Two similar drugs:
-have comparable efficacy and safety

Clinical effectiveness depends on :

• same therapeutic effects
• the time required to reach therapeutic effect.

Two drugs that are bioequivalent may not be therapeutically equivalent.

Question 4

Factors influence bioavailability

Answer 4

1. Solubility of drugs
   - hydrophilic drugs are poorly absorbed due to inability to cross the lipid-rich cell membranes
   - Lipid soluble drugs are readily absorbed result in increased bioavailability.
2. Chemical instability
   -result in decrease bioavailability
   Exp: Penicillin G unstable in gastric contents; insulin destroyed in GIT by degardative enzyme.
3. Nature of the drug formulation
   - rate of absorption based on: particle size, enteric coating and salt form/crystals.
4. First pass hepatic metabolism
   - a phenomenon of drug Metabolism whereby the concentration of drugs is greatly reduced before it reaches the systemic circulation caused by enzyme of liver and gut wall.
   - higher first pass metabolism, decreased bioavailability
   - depend on route of administration

Question 5

Advantage and disadvantage of oral route

Drug formulation & example

Answer 5

Advantages:

1. Easily self-administered
2. Limit number of systemic infections
3. Toxicities can be overcome by antidotes

Disadvantages:

1. High first pass metabolism, low bioavailability
2. Harsh GI environment that lower absorption.
3. Slow onset of action
4. Not useful in emergency, unconscious and Vomitting patients

Drug formulations : Tablet (penicillin) , capsule (Amoxicillin) , syrups (Amoxicillin syrups)

Question 6

Sublingual routes

Answer 6

Advantages:

1. Rapid onset of action
2. Low incidence of infection
3. Avoidance of harsh GI environment
4. Avoid first pass metabolism

Disadvantages :
1. Unpleasant taste of some drugs

Drug formulations : tablets (Nifedipine, Nitroglycerin)

Question 7

Rectal routes

Answer 7

Advantages:

1. Useful in emergency, Vomitting and unconscious patients
2. Biotransformation of drugs by the liver is minimized.
3. Preventing destruction of the drug by intestinal enzymes

Disadvantages :

1. Absorption is erratic and incomplete
2. Irritate the rectal mucosa
3. Uncomfortable/embarrassing for patients.

Drug formulations : suppository
Exp: laxative, paracetamol, diazepam

Question 8

Parenteral routes

Answer 8

Advantages:

1. Avoid the first pass metabolism, 100% bioavailability.
2. Rapid onset of action
3. Useful in unconscious, Vomitting and emergency.

Disadvantages :

1. Induce hemolysis
2. Painful at the site of injection
3. Risk of embolism.

Drug formulation:
Vial: heparin
Ampoule: Gentamicin

Question 9

Inhalation route

Answer 9

Advantages:

1. Avoid first pass metabolism
2. Rapid onset of action
3. Self-administered.

Disadvantages :
1. Bronchial irritation leads to Bronchial and salivary secretion

Drug formulations:
Metered dose inhalers(MDI)
Spacer with inhaler
Exp: salbutamol, budesonide

Question 10

Drug formulation of topical

Answer 10

Drug formulation:
cream (clotrimazole)-treating dermatophytosis ;

drops (atropine) (tropicamide) - to dilate pupil and measurement of refractive errors

Question 11

Transdermal route

Answer 11

Advantages :

1. Avoids the first pass metabolism
2. Slow and sustained release of the drug for prolonged period
3. Convenient for patients

Disadvantages :

1. Local irritation
2. Erythema

Drug formulation: transdermal adhesive patches
Exp: Nitroglycerin, scopolamine, clonidine, nicotine, estradiol