ABA Pharmacology Fundamentals 2 — Questions and Answers
Question 1: Which opioid is most appropriate for a patient with renal failure due to its lack of active metabolite accumulation?
- Morphine
- Meperidine
- Fentanyl (Correct answer)
- Codeine
Correct answer: Fentanyl
Fentanyl is preferred in renal failure because it lacks clinically significant active metabolites that accumulate with impaired clearance.
Question 2: The mechanism by which volatile anesthetics produce immobility is primarily through action at:
- NMDA receptors in the cortex
- GABA-A receptors in the cortex
- Glycine and GABA-A receptors in the spinal cord (Correct answer)
- Nicotinic receptors in the neuromuscular junction
Correct answer: Glycine and GABA-A receptors in the spinal cord
Immobility produced by volatile anesthetics is primarily mediated by enhanced inhibitory signaling at glycine and GABA-A receptors in the spinal cord dorsal horn.
Question 3: A patient on chronic phenytoin therapy requires higher doses of rocuronium. This is best explained by:
- Increased acetylcholinesterase activity
- Upregulation of acetylcholine receptors
- Induction of hepatic CYP enzymes accelerating rocuronium metabolism (Correct answer)
- Competitive antagonism at the nicotinic receptor
Correct answer: Induction of hepatic CYP enzymes accelerating rocuronium metabolism
Phenytoin induces hepatic CYP enzymes, accelerating the metabolism of rocuronium and reducing its duration and potency.
Question 4: Which pharmacokinetic parameter best predicts the duration of action of a single bolus dose of a highly lipophilic drug like thiopental?
- Elimination half-life
- Volume of distribution (Correct answer)
- Clearance
- Bioavailability
Correct answer: Volume of distribution
With highly lipophilic drugs like thiopental, redistribution into peripheral tissues (reflected by volume of distribution) terminates the effect of a single bolus, not elimination.
Question 5: Succinylcholine causes hyperkalemia by which mechanism?
- Inhibiting the Na+/K+ ATPase pump
- Blocking potassium channels in muscle
- Causing prolonged depolarization and potassium efflux through ACh receptors (Correct answer)
- Stimulating aldosterone secretion
Correct answer: Causing prolonged depolarization and potassium efflux through ACh receptors
Succinylcholine depolarizes the motor end plate, and potassium leaks out through persistently open ACh receptor channels, raising serum potassium.
Question 6: The context-sensitive half-time of remifentanil is unique because it:
- Increases steeply with infusion duration due to high lipophilicity
- Remains short regardless of infusion duration due to ester hydrolysis (Correct answer)
- Is prolonged in patients with pseudocholinesterase deficiency
- Depends entirely on renal clearance
Correct answer: Remains short regardless of infusion duration due to ester hydrolysis
Remifentanil is metabolized by nonspecific plasma and tissue esterases, so its context-sensitive half-time remains approximately 3–5 minutes regardless of infusion duration.
Question 7: Which property of local anesthetics determines the speed of onset of nerve block?
- Protein binding
- pKa relative to tissue pH (Correct answer)
- Lipid solubility
- Molecular weight
Correct answer: pKa relative to tissue pH
The pKa determines the fraction of un-ionized (neutral) drug at physiologic pH; a pKa closer to 7.4 means more un-ionized drug available to cross the nerve membrane, speeding onset.
ABA Pharmacology Fundamentals 2
Which opioid is most appropriate for a patient with renal failure due to its lack of active metabolite accumulation?