FACEM Pharmacology Fundamentals 2 — Questions and Answers
Question 1: Which pharmacokinetic parameter describes the fraction of an administered drug that reaches systemic circulation unchanged?
- Volume of distribution
- Bioavailability (Correct answer)
- Clearance
- Half-life
Correct answer: Bioavailability
Bioavailability (F) is the fraction of administered drug that reaches systemic circulation unchanged, accounting for absorption and first-pass metabolism.
Question 2: A patient with severe hepatic failure receives morphine. The most significant pharmacokinetic change expected is:
- Decreased volume of distribution
- Reduced first-pass metabolism increasing bioavailability (Correct answer)
- Accelerated renal clearance
- Increased protein binding
Correct answer: Reduced first-pass metabolism increasing bioavailability
Severe hepatic failure impairs first-pass metabolism, dramatically increasing the oral bioavailability of drugs like morphine.
Question 3: Which receptor type mediates the bronchodilatory effects of salbutamol?
- Alpha-1 adrenoceptor
- Beta-1 adrenoceptor
- Beta-2 adrenoceptor (Correct answer)
- Muscarinic M3 receptor
Correct answer: Beta-2 adrenoceptor
Salbutamol is a selective beta-2 adrenoceptor agonist that causes bronchial smooth muscle relaxation and bronchodilation.
Question 4: The concept of 'therapeutic index' is best defined as:
- The dose required for 50% of the population to respond
- The ratio of the toxic dose to the effective dose (TD50/ED50) (Correct answer)
- The maximum plasma concentration achieved after dosing
- The time to reach steady-state concentration
Correct answer: The ratio of the toxic dose to the effective dose (TD50/ED50)
The therapeutic index is TD50/ED50; a narrow therapeutic index means toxic and therapeutic doses are close together, requiring careful monitoring.
Question 5: A competitive antagonist at the opioid receptor would be expected to:
- Permanently block the receptor regardless of agonist concentration
- Shift the agonist dose-response curve to the right with an unchanged maximum (Correct answer)
- Decrease the maximum response achievable by the agonist
- Activate the receptor with lower intrinsic efficacy than the agonist
Correct answer: Shift the agonist dose-response curve to the right with an unchanged maximum
Competitive antagonists shift the dose-response curve rightward (increasing ED50) but the maximum effect is preserved if enough agonist is present.
Question 6: Which enzyme is primarily responsible for the metabolism of succinylcholine in plasma?
- Cytochrome P450 3A4
- Plasma cholinesterase (pseudocholinesterase) (Correct answer)
- Monoamine oxidase
- Glucuronyl transferase
Correct answer: Plasma cholinesterase (pseudocholinesterase)
Succinylcholine is rapidly hydrolyzed by plasma cholinesterase (pseudocholinesterase); deficiency of this enzyme causes prolonged paralysis.
Question 7: In a patient with end-stage renal failure, which analgesic metabolite accumulates and causes CNS toxicity including seizures?
- Morphine-6-glucuronide
- Norpethidine (normeperidine) (Correct answer)
- Fentanyl-N-oxide
- Buprenorphine-3-glucuronide
Correct answer: Norpethidine (normeperidine)
Norpethidine is a renally cleared active metabolite of pethidine (meperidine) that accumulates in renal failure and causes excitatory CNS effects and seizures.
FACEM Pharmacology Fundamentals 2
Which pharmacokinetic parameter describes the fraction of an administered drug that reaches systemic circulation unchanged?