Methotrexate and co-trimoxazole — GPhC CRA MCQ

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HardDrug InteractionsMethotrexate and co-trimoxazoleGPhC CRA

A patient on weekly methotrexate is prescribed co-trimoxazole. What is the most important interaction to flag?

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Correct answer: E — Increased risk of bone marrow suppression

Co-trimoxazole can increase antifolate toxicity with methotrexate. In this vignette, "Increased risk of bone marrow suppression" is the safest single best answer. The other options are less appropriate because they miss the key clinical risk, conflict with UK medicines guidance, or delay needed review.

Reference: BNF