Oseltamivir Oral Suspension Concentration Revised to Ensure Accurate Dosing

Physicians should be aware of important safety changes being made to the antiviral medication oseltamivir phosphate for oral suspension, which is marketed as Tamiflu, to reduce the possibility of medication errors.

The FDA said in a July 11 safety announcement that the concentration of the neuraminidase inhibitor is changing from 12 mg/mL to 6 mg/mL. The agency said the lower concentration is less likely to become frothy when shaken, ensuring an accurate measurement.

Manufacturer Genentech said in a letter to pharmacists (3-page PDF; About PDFs) that it has initiated a take-back program for the 12 mg/mL version of the product, which will no longer be marketed after current supplies are depleted. Distribution of the 6 mg/mL concentration of oseltamivir is expected to begin by the end of July, the FDA said. Genentech's take-back program is intended to reduce overlap between the two products.

The FDA issued a public health alert in 2009 after it received reports of dosing errors with the drug. The agency said at the time that U.S. physicians typically write prescriptions for liquid medications in milliliters or teaspoons, but the dosage recommendations on the package insert of 12 mg/mL oseltamivir were provided in milligrams.

Genentech has addressed that issue by packaging the 6 mg/mL version of oseltamivir with a new measuring device that uses milliliters and updating the dosing table that accompanies the product with a column for milliliters. The product's container labels and carton packaging will be updated to reflect the changes.

Based on those changes, the FDA issued the following information for physicians: