Errors in Prescribing Methotrexate

To the Editor. —We have systematically evaluated prescribing errors for the past 6 years. 1 Recently, we have observed recurrent prescribing errors involving methotrexate for rheumatoid arthritis. Treatment with methotrexate for rheumatoid arthritis usually involves a regimen of onceweekly administration of doses ranging from 2.5 to 35 mg.2,3 Daily administration of methotrexate greatly increases the potential for toxic effects from a given dose, as it does not allow an interval for the cellular recovery from methotrexate depletion of tetrahydrofolate. 4 Significant toxic effects have been reported following daily administration of methotrexate (for as little as 4 days) because of medication errors. 4,5 In the past year we observed five patients (three inpatients and two outpatients) for whom methotrexate prescribing errors occurred. Inpatient 1 was admitted acutely for unstable angina and eventually underwent coronary bypass grafting. His preadmission medications included 7.5 mg of methotrexate once weekly. During his hospitalization, he was