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Chloramphenicol in pregnancy — GPhC CRA MCQ

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HardInfectionsChloramphenicol in pregnancyGPhC CRA

A patient taking methotrexate 15 mg once weekly for rheumatoid arthritis presents a new prescription for co-trimoxazole. They report mouth ulcers and unexplained bruising. What is the most appropriate pharmacy action?

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Correct answer: A — Withhold co-trimoxazole and obtain urgent prescriber or clinical assessment for possible methotrexate toxicity

Co-trimoxazole has antifolate and marrow-suppressive effects that can substantially increase methotrexate toxicity; the methotrexate SmPC advises against concomitant use. Mouth ulcers and unexplained bruising are toxicity warning symptoms, so this is not a routine clarification: supply should be withheld and urgent clinical assessment arranged. Trimethoprim alone is also an antifolate and is not a safe automatic substitute. Methotrexate must remain once weekly.

Reference: Methotrexate 2.5 mg tablets Summary of Product Characteristics: https://www.medicines.org.uk/emc/product/11716/smpc; NHS SPS: Managing interactions with methotrexate: https://www.sps.nhs.uk/articles/managing-interactions-with-methotrexate/