skip to main content

Trimethoprim and methotrexate — GPhC CRA MCQ

Instant feedback + full explanation. One question, done properly.

HardInfectionsTrimethoprim and methotrexateGPhC CRA

A patient taking methotrexate 15 mg once weekly for rheumatoid arthritis is prescribed trimethoprim for UTI. What is the most important interaction to flag?

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

Reveal the answer and explanation

Correct answer: C — Increased risk of methotrexate toxicity and blood dyscrasias

Trimethoprim can increase the risk of methotrexate toxicity, including bone marrow suppression, because both affect folate pathways. The combination should generally be avoided or managed with specialist advice. Patients should be counselled to report sore throat, bruising or mouth ulcers.

Reference: BNF