Methotrexate should not be used for patients with end-stage kidney disease.

Methotrexate is a widely used disease-modifying anti-rheumatic drug. Its effectiveness has been proven in placebo-controlled trials and in comparison with other disease-modifying anti-rheumatic drugs. The pharmacokinetics of methotrexate are highly variable and unpredictable. In patients with normal renal function, the recommended dose in rheumatoid arthritis ranges between 7.5 and 15 mg/week, but in recent years, even dosages up to 25 mg weekly are used. Toxicity includes myelosuppression, gastrointestinal adverse effects, hepatotoxicity and pneumonitis. Renal impairment and age are considered major risk factors for developing methotrexate toxicity, but studies show conflicting results. Whether methotrexate can be administered to patients with end-stage kidney disease has not been formally tested. The present case illustrates the severe side effects of low-dose methotrexate treatment in a patient with end-stage kidney disease. Seven other cases have reported similar and even more severe and irreversible consequences after low-dose regimen. In view of these side effects we strongly recommend to monitor toxicity rigorously in patients with stage 3 or stage 4 kidney disease and not to use methotrexate in patients with stage 5 kidney disease.