Factors that affect drug absorption (Bioavailability)

Question 1

Factors that affect drug absorption (Bioavailability):

Answer 1

1. Routes of drug administration
2. First pass effect
3. drug pH – alkaline is lipid soluble (uncharged form)
4. liver metabolism
5. higher dosage (mg) and drug concentration (% solution)
6. solubility of preparation – increase in solution
7. increase blood flow to the absorbing area – increase absorption
8. wider absorbing surface – greater absorption
9. half-life – time it takes for ½ of the drug to be eliminated at constant rate of 0.693 t ½

Question 2

effect of GI secretions along with the action of gastric HCl which initially change drug molecules followed by liver metabolism

→ oral route

Answer 2

First Pass Effect

Question 3

→ occurs whenever the drug is administered orally, enters the liver, and suffers extensive biotransformation to such an extent that the bioavailability is drastically reduced

Answer 3

First-pass metabolism or first-pass effect or pre-systemic metabolism

Question 4

• amount of time required for plasma concentration of a drug to decrease by 50% after discontinuance of the drug

Answer 4

Half-Life

Question 5

– reflects rapid decline in plasma concentration as the dose of drug is distributed throughout the body

Answer 5

distribution half-life (t ½ alpha)

Question 6

– slower, reflecting metabolism and excretion of the drug

Answer 6

elimination half-life (t ½ beta)

Question 7

when the response of a particular system is measured against increasing concentration of the drug

Answer 7

Graded Dose-Response Relationship

Question 8

– when the dose required to produce a specified response are determined in each member of the population

Answer 8

Quantal Dose-Response Relationship

Question 9

relative rate at which the drug reaches the general blood circulation

Answer 9

Bioavailability

Question 10

Factors that affects Bioavailability:

Answer 10

1. Solubility of the drug in the contents of the stomach
2. Dietary Pattern
3. Tablet Size
4. Quality control in the manufacturing and Drug formulation

Question 11

constant fraction of the drug reaches the blood circulation after any routes

except: IV, IA, IC

Answer 11

First Order Kinetic of Drug absorption

Question 12

100% of the drug reaches the blood circulation after IV, IA, IC

Answer 12

Zero Order Kinetic of Drug Absorption