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Methotrexate and co-trimoxazole — GPhC CRA MCQ

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ModerateDrug InteractionsMethotrexate and co-trimoxazoleGPhC CRA

A patient on weekly methotrexate is prescribed co-trimoxazole for a respiratory infection. The GP asks whether this is safe. What is the most important interaction to flag?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Severe bone marrow suppression risk

Co-trimoxazole can add antifolate toxicity to methotrexate. The best answer addresses the key safety, legal or pharmaceutical care issue in the vignette. The other options would either delay appropriate care, create a new risk, or fail to resolve the issue. This is consistent with the cited UK reference for safe pharmacy practice.

Reference: BNF