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Pharmacotherapy Review & Drug Interactions Flashcards

7 cards from real MTM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Pharmacotherapy Review & Drug Interactions flashcards as text

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

    Answer: INR will increase due to CYP2C9 inhibition

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

  2. Which combination most significantly increases the risk of QT prolongation?

    Answer: Azithromycin + haloperidol

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

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

    Answer: Serum lithium levels

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

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

    Answer: Bioavailability

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

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

    Answer: CYP2C19; omeprazole

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

  6. A patient on methotrexate is prescribed trimethoprim-sulfamethoxazole. What serious interaction must be anticipated?

    Answer: Additive bone marrow suppression and increased methotrexate toxicity

    TMP-SMX inhibits dihydrofolate reductase (same mechanism as methotrexate) and displaces methotrexate from plasma proteins, causing additive myelosuppression and increased toxicity.

  7. Which statement best describes a Type B (idiosyncratic) adverse drug reaction?

    Answer: It is unpredictable, not dose-dependent, and unrelated to the drug's mechanism

    Type B (bizarre) ADRs are unpredictable, not dose-dependent, and cannot be anticipated from the drug's pharmacological actions; they include hypersensitivity and idiosyncratic reactions.