Pharmacology · single question
A patient is taking both methotrexate and adalimumab (Humira) for an autoimmune condition. Which laboratory test is particularly important to monitor, given methotrexate's primary clearance route?
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Correct answer: A. Creatinine (assessing renal function, since methotrexate is renally cleared and impaired renal function increases methotrexate toxicity risk)
Methotrexate is primarily cleared by the kidneys, so monitoring renal function (via serum creatinine) is important to detect impairment that could lead to drug accumulation and increased toxicity risk (including the oral ulceration toxicity discussed elsewhere). Liver function tests are also commonly monitored in patients on long-term methotrexate, given its potential hepatotoxicity.