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Oral methotrexate: risk of a fatal overdose

The packaging of oral methotrexate-based drugs should be improved so as to avoid fatal dosage errors.

Methotrexate is a drug used in oncology or for the treatment of severe forms of rheumatoid arthritis and psoriasis in low weekly doses. An overdose of methotrexate has serious, sometimes fatal, clinical consequences.

In France, at the beginning of 2013, oral methotrexate drugs are available in tablet form. The packaging is flawed in several ways.

Not only do the bottles have no safety cap, which is dangerous and exposes children to a fatal risk in the event of massive accidental ingestion, but nor does the packaging go far enough to help prevent a risk of overdose. Unlike many other drugs, oral methotrexate is taken weekly. A common cause of overdose resulting in frequent fatalities is when the patient takes the weekly dose daily. The design of the packaging does not include a strong enough warning against the risk of confusion and overdose.

Dividing up the weekly dose of oral methotrexate can be useful for some patients who are unable to tolerate a single weekly dose. Precise information on the methods for dividing the weekly dose, as well as packaging suited to a weekly dose that alerts patients and their caregivers effectively, would provide better patient protection.

Health professionals must be vigilant in writing out prescriptions; there needs to be additional information provided on the packaging, and patients and their caregivers must be made fully aware of the risk.

©Prescrire 1 May 2013

"Weekly oral methotrexate therapy: raise awareness of fatal dosing errors" Prescrire Int 2012; 22 (138): 126. (Pdf, subscribers only).

Download the full review.
Pdf, subscribers only

See also:

Weekly methotrexate:
still more deaths
in France in 2011
Prescrire Int 2012;
21 (123): 15.
Pdf, subscribers only

Methotrexate: avoiding
deadly errors
(May 2007)