Mefloquine has a three-week half-life

October 8, 2009

The FDA recently alerted pharmacists to medication error reports about mefloquine (Lariam) prescriptions calling for 250 mg daily rather than the recommended dose of 250 mg weekly for malaria prophylaxis.

Key Points

The Food and Drug Administration recently alerted pharmacists to medication error reports it has received concerning prescriptions written and dispensed for mefloquine (Lariam) "250 mg daily" rather than the recommended dose of 250 mg weekly for malaria prophylaxis. Some of these reported cases resulted in psychiatric adverse events and hospitalization.

Many U.S. pharmacists do not routinely dispense mefloquine. It is approved for the treatment and prophylaxis of malaria during travel to areas where malaria is endemic. Similarly, many U.S. physicians do not frequently write prescriptions for mefloquine. Consequently, when a prescription for mefloquine is warranted, pharmacists can lack familiarity with the drug and medication errors can result.

The package insert for the drug recommends that travelers to malaria-endemic areas take 250 mg (or the appropriate pediatric weight-based dose) once a week, beginning one week before entering a malaria-endemic area and continuing throughout the trip. The regimen should be continued until four weeks after departure from the malaria-endemic area.

It is most important for pharmacists to remember that mefloquine has a long half-life of three weeks. A prescription written or interpreted with a frequency of "once daily" is likely to have been written in error. A pharmacist should call the prescriber to clarify any "once daily" prescription for the drug.

Raichell S. Brown is a safety evaluator in the Division of Medication Error Prevention and Analysis, Office ofSurveillance and Epidemiology, FDA.