APC Pharmacology Fundamentals 4

Question 1

Induction of CYP3A4 by rifampicin would most likely result in:

Accepted Answer

Decreased plasma levels of co-administered CYP3A4 substrates

Answer

CYP3A4 induction increases enzyme activity, accelerating the metabolism of co-administered substrates and reducing their plasma concentrations.

Question 2

The therapeutic effect of an irreversible enzyme inhibitor drug is typically:

Accepted Answer

Prolonged because new enzyme must be synthesised before full function returns

Answer

Irreversible enzyme inhibition persists until new enzyme is synthesised, meaning recovery depends on enzyme turnover rather than drug elimination.

Question 3

A drug's pKa determines its ionisation state. An acidic drug with pKa 4 in an environment with pH 7 will be predominantly:

Accepted Answer

Ionised and poorly absorbed across membranes

Answer

When the pH is much higher than the pKa of an acidic drug, the Henderson-Hasselbalch equation predicts the drug will be predominantly ionised and less able to cross lipid membranes.

Question 4

Which of the following statements about bioavailability is correct?

Accepted Answer

Bioavailability compares the AUC of a given route to IV administration (AUC = 100%)

Answer

Absolute bioavailability (F) is the fraction of an administered dose that reaches systemic circulation, calculated by comparing AUC of the route to IV (F=100%) administration.

Question 5

Receptor upregulation commonly occurs in response to:

Accepted Answer

Chronic antagonist exposure or receptor blockade

Answer

Prolonged receptor blockade by an antagonist can lead to upregulation (increased number or sensitivity) of receptors as a compensatory mechanism.

(APC) Australian Pharmacy Council Practice Test

(APC) Australian Pharmacy Council Practice Test

APC Pharmacology Fundamentals 4