Genentech Plans Tamiflu Buy-back After Changing Concentration Of Oral Solution

Distribution of the new 6 mg/mL oral solution concentration will begin this month, but 12 mg/mL concentration products can still be used until they expire, FDA says.

Genentech plans a buy-back program to hasten the phase-out of its higher concentration Tamiflu (oseltamivir phosphate) oral suspension.

The oral suspension of the influenza drug will be distributed in 6 mg/mL concentrations beginning this month, ending the availability of the 12 mg/mL concentration product once supplies run out.

The concentration change was instituted in part because the lower concentration is less likely to become "frothy" when shaken and ensures a more accurate measurement, the agency said in a safety communication. The product must be shaken well before each use, according to the label.

FDA announced a labeling and concentration change July 11 to reduce the possibility of prescribing errors and dosing confusion. The agency said there are no quality problems associated with the previous higher concentration and the products are still usable until their expiration date.

As such, the higher concentration version is expected to remain in the marketplace and national stockpiles until the bottles expire, though the company estimates a minimal supply of the 12 mg/mL oral suspension remains at pharmacies and distributors.

The agency is encouraging wholesalers, distributors and pharmacies to participate in Genentech's voluntary buy-back program to limit the potential for confusion.

Pharmacists were asked to contact their distributors by Aug. 31 to determine whether unused 12 mg/mL Tamiflu is eligible for the buy-back program.

Genentech is not replacing 12 mg/mL bottles with new 6 mg/mL bottles, a company spokesperson said. Instead, it plans to refund 90% of the wholesale acquisition cost (WAC), reimburse ground-shipping costs and pay $1.19 processing fee per bottle returned.

The WAC for one bottle of the new concentration is $93.12; the current WAC for a bottle of the old concentration is $42.71.

Changing The Dosing Device

In addition to changing the concentration, the new version of Tamiflu's oral solution will have a new dosing device with measurements in milliliters instead of milligrams, and the dosing table in the label will include a column for the volume based on the new concentration. Containers and packaging also will be adjusted, along with compounding instructions, to reflect the concentration change, according to the safety communication.

FDA approved the supplement to change the label on March 21. It likely stemmed in part from a September 2009 public health alert that was issued after the agency received reports of errors where dosing instructions did not match the measurements on the dose dispenser. The agency also said the commercial oral suspension concentrations were different from those produced by compounding pharmacies for emergency use.

Prescribers were reminded that patients could receive either concentration during the upcoming flu season and should write prescriptions for the new oral suspension concentration with doses in milliliters.

Pharmacists also were advised to ensure each Tamiflu prescription includes a concentration and dose and clarify with the prescriber if they are not listed. They also were asked to verify that the unit of measurement used matches the provided dosing device.

-Derrick Gingery ([email protected])