KAPS Pharmacology Fundamentals 3 — Questions and Answers
Question 1: A drug that blocks the effects of an agonist by binding to an allosteric site on the receptor (not the active site) is best described as:
- Competitive antagonist
- Non-competitive antagonist (Correct answer)
- Physiological antagonist
- Chemical antagonist
Correct answer: Non-competitive antagonist
Non-competitive antagonists bind to allosteric sites, changing receptor conformation and reducing the maximal effect of the agonist regardless of agonist concentration.
Question 2: Which of the following best defines 'apparent volume of distribution' (Vd)?
- The actual physical volume of plasma in the body
- A hypothetical volume in which a drug would need to be uniformly distributed to account for its plasma concentration (Correct answer)
- The volume of tissue where the drug binds to receptors
- The volume of urine excreted per unit time
Correct answer: A hypothetical volume in which a drug would need to be uniformly distributed to account for its plasma concentration
Vd is a theoretical volume that relates the total amount of drug in the body to the drug concentration measured in plasma.
Question 3: A patient taking Drug A (a CYP3A4 inhibitor) begins a new prescription for Drug B (a CYP3A4 substrate). What is the most likely outcome?
- Decreased plasma levels of Drug B
- Increased plasma levels of Drug B (Correct answer)
- No change in Drug B plasma levels
- Accelerated renal clearance of Drug B
Correct answer: Increased plasma levels of Drug B
CYP3A4 inhibition reduces the metabolism of Drug B, causing it to accumulate and reach higher plasma concentrations.
Question 4: Which receptor superfamily uses a G-protein coupled mechanism where the activated receptor indirectly regulates ion channels or enzymes?
- Ligand-gated ion channels
- GPCRs (metabotropic receptors) (Correct answer)
- Nuclear receptors
- Receptor tyrosine kinases
Correct answer: GPCRs (metabotropic receptors)
G-protein coupled receptors (GPCRs) are metabotropic receptors that activate intracellular G-proteins to modulate second messengers and downstream effectors.
Question 5: Renal clearance of a drug is reduced in a patient with kidney disease. What adjustment is typically required?
- Increase the dose to compensate for reduced absorption
- Decrease the dose or increase the dosing interval (Correct answer)
- Switch to a hepatically metabolized drug without adjustment
- Administer the drug intravenously instead of orally
Correct answer: Decrease the dose or increase the dosing interval
Reduced renal clearance means the drug accumulates, so the dose should be reduced or the interval extended to avoid toxicity.
Question 6: Which pharmacodynamic concept describes the relationship between receptor occupancy and the resulting biological effect?
- Potency
- Efficacy
- Dose-response curve
- Stimulus-response coupling (Correct answer)
Correct answer: Stimulus-response coupling
Stimulus-response coupling (or receptor-effector coupling) describes the relationship between receptor occupancy and the magnitude of biological response, which is often non-linear.
Question 7: Aspirin irreversibly inhibits cyclooxygenase (COX). What is the pharmacological term for this type of inhibition?
- Competitive inhibition
- Reversible non-competitive inhibition
- Covalent (irreversible) inhibition (Correct answer)
- Allosteric activation
Correct answer: Covalent (irreversible) inhibition
Aspirin acetylates and permanently inactivates COX enzymes via covalent bond formation, making this an irreversible inhibition.
KAPS Pharmacology Fundamentals 3
A drug that blocks the effects of an agonist by binding to an allosteric site on the receptor (not the active site) is best described as: