GAMSAT Pharmacology Fundamentals 3 — Questions and Answers
Question 1: A partial agonist differs from a full agonist primarily because it:
- Binds to a different receptor subtype
- Produces a lower maximal effect even when all receptors are occupied (Correct answer)
- Has a lower affinity for the receptor
- Requires a longer duration to produce its effect
Correct answer: Produces a lower maximal effect even when all receptors are occupied
A partial agonist has intrinsic efficacy less than 1, so even at full receptor occupancy it cannot achieve the maximal response that a full agonist produces.
Question 2: Which route of administration completely bypasses first-pass metabolism?
- Oral (swallowed tablet)
- Sublingual (Correct answer)
- Rectal suppository (lower rectum)
- Enteric-coated oral capsule
Correct answer: Sublingual
Sublingual administration delivers drug directly into the systemic venous circulation via the oral mucosa, entirely avoiding portal circulation and hepatic first-pass metabolism.
Question 3: Drug A has a half-life of 8 hours. Approximately how long will it take to reach steady-state plasma concentration during regular dosing?
- 8 hours
- 16 hours
- 40 hours (Correct answer)
- 80 hours
Correct answer: 40 hours
Steady state is reached after approximately 4–5 half-lives; 5 × 8 h = 40 h is the standard approximation used clinically.
Question 4: Which of the following best describes the mechanism of non-competitive (irreversible) antagonism?
- The antagonist competes with the agonist for the same binding site and can be displaced
- The antagonist covalently binds to the receptor, permanently reducing the number of functional receptors (Correct answer)
- The antagonist increases the agonist's affinity for the receptor
- The antagonist acts on a separate receptor to produce opposite physiological effects
Correct answer: The antagonist covalently binds to the receptor, permanently reducing the number of functional receptors
Irreversible antagonists form covalent bonds with the receptor, permanently inactivating it so that even large concentrations of agonist cannot restore the maximal effect.
Question 5: Bioavailability is defined as the fraction of administered drug that:
- Crosses the blood-brain barrier
- Reaches systemic circulation in unchanged, active form (Correct answer)
- Binds to plasma proteins and is transported to target tissues
- Is excreted unchanged in the urine
Correct answer: Reaches systemic circulation in unchanged, active form
Bioavailability (F) represents the proportion of an administered dose that reaches systemic circulation intact and is available to exert pharmacological effects.
Question 6: A highly lipophilic drug is administered orally. Which property is most likely to result in a high volume of distribution?
- High water solubility promoting renal excretion
- Extensive plasma protein binding trapping the drug in blood
- Accumulation in adipose tissue and other peripheral compartments (Correct answer)
- Rapid hepatic metabolism before distribution
Correct answer: Accumulation in adipose tissue and other peripheral compartments
Lipophilic drugs readily partition into fat and other tissues, creating high apparent volumes of distribution that greatly exceed actual body fluid volumes.
Question 7: Enterohepatic recirculation of a drug would be expected to:
- Shorten the drug's effective half-life
- Prolong the drug's duration of action by returning it to systemic circulation (Correct answer)
- Increase renal clearance of the drug
- Reduce the drug's volume of distribution
Correct answer: Prolong the drug's duration of action by returning it to systemic circulation
Enterohepatic recirculation occurs when a drug excreted in bile is reabsorbed from the intestine, recycling it back into systemic circulation and prolonging its half-life and effect.
GAMSAT Pharmacology Fundamentals 3
A partial agonist differs from a full agonist primarily because it: