Low-dose methotrexate therapy can be used to treat rheumatoid arthritis, asthma, psoriasis, and other inflammatory diseases. When the drug is used for these conditions, the dose is administered weekly or twice a week. Unfortunately, it is not uncommon for the Institute for Safe Medication Practices (ISMP) to receive reports of oral methotrexate overdoses, and even fatalities, due to accidental daily instead of weekly dosing.
In one case, a physician decided to add methotrexate 10 mg weekly to a psoriasis patient's daily prednisone regimen. Methotrexate 2.5 mg tablets were prescribed with instructions to "take 2 tablets on Monday morning and 2 tablets Monday at bedtime."For some reason, the pharmacy label was unclear to the patient. Because her doctor described the methotrexate as "supplemental therapy to her prednisone," the patient assumed that it was to be taken every day with her prednisone. She took 4 tablets (10 mg) daily for 1 week before being admitted to the hospital due to intolerable nausea, vomiting, and diarrhea.
Another report described a patient who was to receive 15 mg of methotrexate weekly. The prescription was written for the 2.5 mg tablets with instructions to take 3 tablets every 12 hours. Unfortunately, the physician mistakenly omitted "once weekly"on the prescription. The pharmacist who processed and dispensed the prescription spoke to the patient and told him that it seemed like a high dose for the conditions for which he was being treated. Nonetheless, the pharmacist reinforced the physician's incorrect directions. After 6 days of treatment, the patient was admitted to the hospital with rectal bleeding, mouth sores, and myalgias.
In yet another report, a patient picked up a refill of what was intended to be a 90-day supply of metoclopramide 5 mg with instructions to take 1/2 tablet (2.5 mg) 4 times daily. The vial, however, contained 360 tablets of methotrexate 2.5 mg instead. The patient did not question the change in tablet appearance. She took the medication as prescribed for several days before she developed internal and external hemorrhaging, which led to a lengthy hospitalization and numerous blood transfusions.
Methotrexate is considered a high-alert medicationa drug that bears a heightened risk of causing significant patient harm when it is used in error. For this reason, extra precautions should be taken when prescribing, dispensing, or administering methotrexate. Clearly, these reports stress the underlying need for health care practitioners to improve patient education efforts. ISMP recommends the following safeguards to reduce the risk of an error when oral methotrexate is prescribed:
Drs. Kelly and Vaida are both with the Institute for Safe Medication Practices (ISMP). Dr. Kelly is the editor of ISMP Medication Safety Alert! Community/ Ambulatory Care Edition, and Dr. Vaida is the executive director of ISMP.
Report Medication Errors
The reports described here were received through the USP Medication Errors Reporting Program, which is presented in cooperation with the Institute for Safe Medication Practices (ISMP). ISMP is a nonprofit organization whose mission is to understand the causes of medication errors and to provide time-critical error-reduction strategies to the health care community, policy makers, and the public. Throughout this series, the underlying system causes of medication errors will be presented to help readers identify system changes that can strengthen the safety of their operation.
If you have encountered medication errors and would like to report them, you may call ISMP at 800-324-5723 (800-FAILSAFE) or USP at 800-233-7767 (800-23-ERROR). ISMP's Web address is www.ismp.org.
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