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Methotrexate and trimethoprim — GPhC CRA MCQ

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HardInfectionsMethotrexate and trimethoprimGPhC CRA

A patient taking weekly methotrexate for rheumatoid arthritis is prescribed trimethoprim for a UTI. She also takes folic acid weekly. What is the most important interaction to flag?

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Correct answer: C — Increased risk of bone marrow suppression

Trimethoprim and methotrexate both affect folate pathways and the combination can increase the risk of serious bone marrow suppression. The prescription should be queried and an alternative antibiotic considered where appropriate. The other options either delay appropriate care, use an unsuitable medicine, or miss the main safety issue.

Reference: BNF; NICE CKS