Master of Pharmacy: Pharmacokinetics and Pharmacodynamics Flashcards
7 cards from real MPharm Master of Pharmacy practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Master of Pharmacy: Pharmacokinetics and Pharmacodynamics flashcards as text
Which of the following best explains why phenytoin exhibits zero-order kinetics at therapeutic doses?
Answer: Its metabolizing enzymes become saturated within the therapeutic range
Phenytoin saturates CYP2C9/CYP2C19 at therapeutic concentrations, so a constant amount (not fraction) is metabolized per unit time — zero-order kinetics.
In the context of pharmacodynamics, receptor reserve (spare receptors) means that:
Answer: Only a fraction of total receptors need to be occupied to produce a maximum response
Receptor reserve exists when a maximum biological response can be achieved by occupying only a small fraction of the total available receptors.
When two drugs are given together and their combined effect is greater than additive, this interaction is termed:
Answer: Synergism
Synergism (or superadditivity) occurs when the combined drug effect exceeds the simple sum of individual effects.
The bioequivalence of two formulations is assessed primarily by comparing:
Answer: AUC and Cmax under standardized conditions
Bioequivalence studies compare AUC (total exposure) and Cmax (peak concentration) between test and reference formulations within 80–125% confidence intervals.
A drug has a hepatic extraction ratio of 0.9. Its oral bioavailability is primarily limited by:
Answer: Extensive first-pass hepatic metabolism
A high extraction ratio (0.9) means 90% of absorbed drug is removed by the liver on first pass, severely limiting systemic bioavailability.
Which pharmacokinetic model assumes that the body behaves as a single homogeneous compartment for drug distribution?
Answer: One-compartment open model
The one-compartment model assumes instantaneous and uniform drug distribution throughout the body, with log-linear decline in plasma concentration.
Upregulation of receptors typically occurs in response to:
Answer: Chronic antagonist blockade or denervation
Prolonged antagonist administration or denervation deprives receptors of stimulation, triggering compensatory upregulation and increased receptor density.