APC Pharmacology Fundamentals 2 — Questions and Answers
Question 1: A drug with a narrow therapeutic index requires careful monitoring because:
- Its onset of action is very rapid
- The difference between therapeutic and toxic concentrations is small (Correct answer)
- It undergoes extensive first-pass metabolism
- It is highly lipid-soluble
Correct answer: The difference between therapeutic and toxic concentrations is small
A narrow therapeutic index means the toxic dose is close to the therapeutic dose, requiring careful dosing and monitoring.
Question 2: Which pharmacokinetic process describes the movement of a drug from the systemic circulation into tissues?
- Absorption
- Distribution (Correct answer)
- Metabolism
- Excretion
Correct answer: Distribution
Distribution refers to the reversible transfer of a drug from the bloodstream into tissues and organs throughout the body.
Question 3: A competitive antagonist differs from a non-competitive antagonist in that it:
- Permanently binds to the receptor
- Can be overcome by increasing the agonist concentration (Correct answer)
- Reduces the maximum response achievable
- Acts at an allosteric site on the receptor
Correct answer: Can be overcome by increasing the agonist concentration
A competitive antagonist competes with the agonist for the same binding site, and its effects can be overcome by increasing agonist concentration.
Question 4: The Vd (volume of distribution) of a highly protein-bound drug that remains in the plasma would be expected to be:
- Very large (>100 L)
- Very small (close to plasma volume, ~3–5 L) (Correct answer)
- Equal to total body water (~42 L)
- Unpredictable
Correct answer: Very small (close to plasma volume, ~3–5 L)
Drugs that are highly plasma protein-bound and do not distribute into tissues have a small Vd approximating plasma volume.
Question 5: Which cytochrome P450 enzyme is responsible for metabolising the greatest number of clinically used drugs?
- CYP1A2
- CYP2D6
- CYP3A4 (Correct answer)
- CYP2C9
Correct answer: CYP3A4
CYP3A4 is the most abundant hepatic CYP enzyme and metabolises approximately 50% of all clinically used drugs.
Question 6: An inverse agonist at a receptor will:
- Produce the same effect as the full agonist but less potently
- Block the receptor without producing any effect
- Produce an effect opposite to that of the agonist (Correct answer)
- Increase the affinity of the agonist for its receptor
Correct answer: Produce an effect opposite to that of the agonist
An inverse agonist binds the receptor and produces an effect opposite in direction to that of the agonist, reducing basal receptor activity.
Question 7: Phase II drug metabolism reactions primarily involve:
- Oxidation, reduction, and hydrolysis
- Conjugation of the drug or its metabolite with an endogenous molecule (Correct answer)
- CYP450-mediated hydroxylation
- Hydrolysis of ester bonds only
Correct answer: Conjugation of the drug or its metabolite with an endogenous molecule
Phase II reactions are conjugation reactions (e.g., glucuronidation, sulfation, acetylation) that increase water solubility to facilitate excretion.
APC Pharmacology Fundamentals 2
A drug with a narrow therapeutic index requires careful monitoring because: