MTM Pharmacotherapy Review & Drug Interactions 2

Question 1

A patient on warfarin begins fluconazole therapy. What is the expected effect on INR?

Accepted Answer

INR will increase due to CYP2C9 inhibition

Answer

Fluconazole inhibits CYP2C9, the primary enzyme responsible for warfarin (S-enantiomer) metabolism, leading to elevated warfarin levels and increased INR.

Question 2

Which combination most significantly increases the risk of QT prolongation?

Accepted Answer

Azithromycin + haloperidol

Answer

Both azithromycin and haloperidol independently prolong the QT interval, and their combination significantly raises the risk of torsades de pointes.

Question 3

A patient takes lithium and is started on ibuprofen for pain. What monitoring is most critical?

Accepted Answer

Serum lithium levels

Answer

NSAIDs reduce renal prostaglandin synthesis, decreasing renal blood flow and lithium clearance, which can lead to lithium toxicity.

Question 4

Which pharmacokinetic parameter best describes the fraction of a drug that reaches systemic circulation unchanged?

Accepted Answer

Bioavailability

Answer

Bioavailability (F) represents the fraction of an administered dose that reaches the systemic circulation in active form.

Question 5

Clopidogrel requires activation by which enzyme, and what common drug inhibits this conversion?

Accepted Answer

CYP2C19; omeprazole

Answer

Clopidogrel is a prodrug activated by CYP2C19; omeprazole inhibits CYP2C19 and can reduce active metabolite formation, diminishing antiplatelet effect.

(MTM) Medication Therapy Management Board Certification Practice Test

(MTM) Medication Therapy Management Board Certification Practice Test

MTM Pharmacotherapy Review & Drug Interactions 2