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Methotrexate toxicity — SCE Rheumatology MCQ

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HardRheumatoid arthritisMethotrexate toxicitySCE Rheumatology

A 55-year-old woman with seropositive rheumatoid arthritis has recurrent mouth ulcers and bruising after taking methotrexate daily by mistake for 10 days. FBC shows neutrophils 0.6 × 10^9/L, platelets 54 × 10^9/L and creatinine has risen from 72 to 156 µmol/L after trimethoprim for a urinary infection. What is the most appropriate immediate management?

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Correct answer: C — Stop methotrexate and give folinic acid rescue with urgent admission

This is methotrexate toxicity, amplified by daily dosing error, renal impairment and trimethoprim interaction. Management requires urgent admission, cessation of methotrexate and folinic acid rescue with infection assessment and haematology input as needed. Folic acid supplementation is preventative, not adequate treatment for severe cytopenias.

Reference: BNF; BSR csDMARD monitoring guideline 2025