2. Pharmacokinetics and Pharmacodynamics

Question 1

Phases in drug-body interactions

Answer 1

Absorption
Clinical effect
Metabolism
Excretion

Question 2

Routes of drug administration and examples (2)

Answer 2

Enteral (via gut - oral)

Parenteral (IV, IM, SC, TD, inhalation)

Question 3

Advantages of oral drug administration

Answer 3

Socially acceptable

Question 4

Disadvantages of oral drug administration (4)

Answer 4

Slow onset
Variable absorption
First-pass metabolism
Least reliable

Question 5

Factors accepting oral absorption (5)

Answer 5

Lipid solubility
Drug formulation
GI motility
Interactions with other substances in the gut
GIT disease

Question 6

Definition and effect of first-pass metabolism (2)

Answer 6

Orally administered drugs can reach systemic circulation after passing through the liver once
Alters drug concentration

Question 7

Types of liver metabolism, effect and example (2)

Answer 7

Drug inactivation - more required orally for desired effect, GTN
Drug activation - activates inactive form. Acyclovir

Question 8

Advantages of parenteral drug administration (2)

Answer 8

Predictable plasma levels (when administered)

No first-pass metabolism

Question 9

Disadvantages of parenteral drug administration (3)

Answer 9

More severe allergic reaction
Access difficulties/self-medication
Higher drug costs

Question 10

Definition of bioavailability

Answer 10

Proportion of ingested drug available for clinical effect

Question 11

Bioavailability is modified by (4)

Answer 11

Dosage form
Destruction in the gut
Poor absorption
First-pass metabolism

Question 12

Explanation of volume of distribution

Answer 12

How much of the body the drug is diluted in (different compartments)

Question 13

Drug distribution is affected by (2)

Answer 13

Lipid binding - slow release from accumulation

Drug binding to plasma proteins (bound drug is inactive)

Question 14

Definition of drug metabolism

Answer 14

Preparing drug for elimination from the body

Question 15

Action and definitions of drug metabolism (2)

Answer 15

Phase 1 reactions - inactivates drugs

Phase 2 reactions - prepares for removal/removes from body

Question 16

Types of phase 1 reactions (3)

Answer 16

Oxidation, reduction, hydrolysis

Question 17

Types of phase 2 reactions

Answer 17

Conjugation - glucuronidation, sulfanation, methylation, acetylation, glutathione

Question 18

Methods of drug excretion 4)

Answer 18

Renal (urine) - via RAAS
Liver (bile)
Lungs (gas exchange)
Others (Sweat, saliva)

Question 19

Excretion disorders (2) and examples (2)

Answer 19

Renal disease - chronic renal failure

Liver disease - liver failure

Question 20

Drug distribution compartment definitions (2)

Answer 20

Single compartment model - drug behaves as if evenly distributed throughout body
Two-compartment model - drug behaves as if in equilibrium with different body tissues

Question 21

Pharmacokinetics involves (2)

Answer 21

Drug clearance

Repeated drug dosing

Question 22

What does drug clearance involve (2)

Answer 22

Plasma half-life (t0.5)

First order kinetics/zero order kinetics

Question 23

First order kinetics (4):
Active/passive
Elimination vs concentration
Graph
Plasma half life

Answer 23

Drug elimination/absorption is passive diffusion
Drug elimination is proportional to drug concentration
Logarithmic graph of elimination is a straight line
Plasma half-life is constant

Question 24

Zero order kinetics (3):
Active/passive
Elimination vs concentration
Graph

Answer 24

Drug elimination is active and can be saturated by very high drug concentrations
Max. rate of elimination is constant regardless of concentration
Linear graph of drug elimination (constant amount eliminated per unit time)

Question 25

Definition of drug accumulation

Answer 25

How the plasma concentration builds if repeated doses of a drug are given

Question 26

Drug scheduling issues (2)

Answer 26

Too frequent - plasma levels may become toxic

Too infrequent - sub-therapeutic plasma levels and no clinical effect