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Methotrexate and trimethoprim — GPhC CRA MCQ

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HardMusculoskeletal TherapeuticsMethotrexate and trimethoprimGPhC CRA

A patient taking weekly methotrexate for psoriasis is prescribed trimethoprim for UTI. They ask if it is safe because both are tablets. 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: A — Increased antifolate toxicity and bone marrow suppression risk

Trimethoprim can add to methotrexate antifolate toxicity. 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; NICE CKS