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

Increased plasma levels of co-administered CYP3A4 substrates

Answer

Inhibition of the metabolism of co-administered drugs

Answer

No clinically significant drug interactions

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

Short-lived because the drug is rapidly excreted

Answer

Reversed by administering a competitive agonist

Answer

Limited to the duration of drug-receptor binding

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

Unionised and well absorbed

Answer

Equally ionised and unionised

Answer

Fully unionised regardless of pH

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

Intravenous bioavailability is defined as 50%

Answer

Oral bioavailability can exceed 100% due to enterohepatic recycling

Answer

Bioavailability is only affected by intestinal absorption

Question 5

Receptor upregulation commonly occurs in response to:

Accepted Answer

Chronic antagonist exposure or receptor blockade

Answer

Chronic agonist exposure

Answer

Allosteric modulation

Answer

Phase I metabolism

Question 6

What does EC50 represent in a dose-response curve?

Accepted Answer

The concentration producing 50% of the maximum effect

Answer

The dose that produces 50% lethality in a population

Answer

The concentration at which the drug is 50% protein-bound

Answer

The dose required to occupy 50% of all available receptors

Question 7

A pharmacist notes that a patient's drug has high hepatic extraction ratio. This means:

Accepted Answer

The liver removes a large proportion of drug during first-pass, resulting in low oral bioavailability

Answer

The drug is poorly absorbed from the gut

Answer

The drug requires dose reduction in renal impairment only

Answer

The drug has a large volume of distribution