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Methotrexate and co-trimoxazole — GPhC CRA MCQ

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HardDrug InteractionsMethotrexate and co-trimoxazoleGPhC CRA

A patient on methotrexate is prescribed co-trimoxazole and reports mouth ulcers with unusual tiredness. What monitoring is required?

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Correct answer: E — Check full blood count urgently and avoid routine supply

Co-trimoxazole with methotrexate can cause severe bone marrow suppression, requiring urgent monitoring and review. This makes check full blood count urgently and avoid routine supply the single best answer in this scenario. The other options would either miss the key safety issue, delay appropriate review, or fail to meet the relevant clinical or professional requirement.

Reference: BNF interactions