PTCB Pharmacology #3 3

Question 1

Which CYP enzyme is responsible for metabolizing the largest proportion of drugs?

Accepted Answer

CYP3A4

Answer

CYP3A4 is the most abundant hepatic cytochrome P450 enzyme, responsible for metabolizing approximately 50% of all drugs, including statins, benzodiazepines, calcium channel blockers, and many others.

Question 2

A CYP enzyme "inducer" would be expected to:

Accepted Answer

Decrease plasma levels of co-administered drugs metabolized by that enzyme

Answer

Enzyme inducers (e.g., rifampin, carbamazepine, St. John's Wort) increase CYP enzyme expression, accelerating metabolism and DECREASING plasma levels of affected drugs, potentially causing therapeutic failure.

Question 3

Which of the following is a major contraindication for the use of metformin?

Accepted Answer

eGFR < 30 mL/min/1.73m² (severe renal impairment)

Answer

Metformin is contraindicated in severe renal impairment (eGFR < 30) due to the risk of lactic acidosis from reduced elimination. It should be used cautiously when eGFR is 30–45 and is generally avoided when < 30.

Question 4

Grapefruit juice interacts with many drugs because it:

Accepted Answer

Inhibits intestinal CYP3A4 and P-glycoprotein

Answer

Grapefruit juice contains furanocoumarins that irreversibly inhibit CYP3A4 in the intestinal wall and P-gp, increasing bioavailability of many drugs (statins, calcium channel blockers, immunosuppressants).

Question 5

Which drug class do "-gliptin" suffix drugs belong to?

Accepted Answer

DPP-4 inhibitors

Answer

DPP-4 inhibitors (dipeptidyl peptidase-4 inhibitors) end in "-gliptin" (sitagliptin, saxagliptin, alogliptin, linagliptin). They prolong incretin activity, enhancing glucose-dependent insulin secretion.

Pharmacy Practice Test

Pharmacy Practice Test

PTCB Pharmacology #3 3