Pharmacology Fundamentals Flashcards

Which mechanism best explains the tachyphylaxis seen with repeated doses of ephedrine?

Answer: Depletion of noradrenaline from presynaptic vesicles

Ephedrine acts indirectly by displacing noradrenaline from presynaptic terminals; repeated dosing depletes these stores, reducing each subsequent response.

Rocuronium's neuromuscular blockade is antagonised by sugammadex via which mechanism?

Answer: Encapsulation of rocuronium molecules reducing free plasma concentration

Sugammadex is a modified gamma-cyclodextrin that encapsulates rocuronium (and vecuronium) in a tight complex, removing it from plasma and reversing blockade.

A therapeutic drug monitoring level is taken 6 hours after an IV dose of vancomycin. The result is best described as:

Answer: An area-under-the-curve surrogate correlating with bactericidal activity

Modern vancomycin monitoring uses AUC/MIC ratio as the pharmacodynamic target; a mid-interval level can be used to estimate AUC when combined with another sample.

Which pharmacodynamic parameter is most predictive of beta-lactam antibiotic efficacy?

Answer: Time above MIC (%T>MIC)

Beta-lactams exhibit time-dependent bactericidal activity; efficacy correlates with the proportion of the dosing interval during which free drug concentration exceeds the MIC.

A critically ill patient develops prolonged paralysis after a single intubating dose of suxamethonium. The most likely cause is:

Answer: Pseudocholinesterase deficiency reducing hydrolysis of suxamethonium

Suxamethonium is hydrolysed by plasma pseudocholinesterase (butyrylcholinesterase); deficiency — genetic or acquired — prolongs the duration of blockade from minutes to hours.

Which statement about propofol pharmacokinetics in critically ill patients is correct?

Answer: Its large volume of distribution means context-sensitive half-time rises markedly with prolonged infusions

Propofol's high lipophilicity and large Vd cause redistribution from deep tissue compartments after prolonged infusions, markedly increasing context-sensitive half-time.

Non-depolarising neuromuscular blocking agents are monitored at the adductor pollicis. Which train-of-four (TOF) ratio confirms adequate reversal before extubation?

Answer: TOF ratio ≥ 0.9

A TOF ratio ≥ 0.9 at the adductor pollicis is the current standard for confirming adequate neuromuscular recovery before extubation.