Pancytopenia induced by low-dose methotrexate for rheumatoid arthritis.

Four cases of pancytopenia related to low-dose weekly pulse methotrexate therapy for rheumatoid arthritis are described. All patients were aged above 60 years and had renal impairment. In every case marrow recovery followed withdrawal of methotrexate. However, one patient developed pneumonitis and died. Cholangitis, respiratory infection and increase in methotrexate dose were precipitating factors. Pharmacokinetic data indicated prolonged tissue drug exposure in two cases studied; dose-related toxicity was further supported by successful resumption of methotrexate in reduced dosage in two cases. It is possible that methotrexate dose should be modified during intercurrent illness in patients older than 60 years who have renal impairment.