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Methotrexate toxicity — RCPSC IM MCQ

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HardRheumatologyMethotrexate toxicityRCPSC IM

A patient taking methotrexate develops mucositis, pancytopenia and acute kidney injury after trimethoprim-sulfamethoxazole. What is the best immediate response?

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Correct answer: B — Stop both drugs and begin urgent toxicity management

The best answer is “Stop both drugs and begin urgent toxicity management”. Trimethoprim-sulfamethoxazole potentiates methotrexate antifolate toxicity and impaired clearance worsens exposure. Both drugs are stopped and severe cytopenia, infection risk, renal function and folinic-acid rescue are assessed urgently. Folinic acid, growth-factor support and antimicrobial treatment are selected according to severity, while counts and renal function are followed closely.

Reference: Canadian Rheumatology Association, clinical guidelines: https://rheum.ca/resources/publications/