Medication errors with methotrexate: new insights into an old drug
Methotrexate (MTX) was first used in 1948 to treat childhood leukaemia. Nowadays, it is used for the treatment of inflammatory diseases, such as rheumatoid arthritis (RA), psoriasis, psoriatic arthritis and inflammatory bowel disease. MTX is a folic acid antagonist that binds dihydrofolate reductase and thereby inhibits the synthesis of deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and proteins.
As an incontestable cornerstone in the treatment of RA, MTX should be started as soon as RA is diagnosed. The primary goal of the treatment is rapid and effective disease control to prevent long-term damage to the joints. For the treatment of patients with RA, the usual starting dose of MTX is 7.5-10 mg per week. Based on the clinical response, the dose could be increased to reach the optimal dose. The most common adverse drug events of MTX therapy are gastro-intestinal intolerance, haematological abnormalities, alopecia, hepatotoxicity and pulmonary toxicity.
Overall, MTX is well tolerated. However, fatal cases of MTX intoxication have been reported in literature, mainly due to the daily intake and thus overdose of MTX.
Despite the widespread experience with MTX, medication errors still occur with a risk of potentially severe adverse drug events. Clinical pharmacy interventions aim to detect these medication errors in inpatients. Based on a case series within a hospital population, the most common medication errors with MTX are presented. Subsequently, specific interventions to optimize medication safety with MTX therapy are described. The implementation of a specific chemotherapy module in the computerized physician order entry and clinical pharmacy interventions, such as medication reconciliation, the engagement of clinical pharmacists on hospital wards as part of the interdisciplinary team and prescription validation based on clinical rules, can contribute to a safer use of MTX.
