Tamiflu concentration change aids dosing accuracy

Genentech and the FDA have revised the concentration of Tamiflu for oral suspension in an attempt for more accurate dosing. Although the changes are being made to reduce the possibility of prescribing and dosing confusion that can lead to medication errors, some confusion is likely next flu season because both old and new concentrations will be on the market simultaneously.

The concentration will drop to 6 milligrams per milliliter from the current 12 mg/mL. The lower concentration is less likely to become frothy when shaken, which helps to ensure an accurate measurement, according to an announcement. The 12 mg/mL concentration will no longer be marketed after current supplies run out.

Genentech and the FDA are revising labeling and packaging to reflect the change. They're also revising the compounding instructions for pharmacies in the event of a Tamiflu shortage, in which case pharmacists will make the 6-mg/mL oral suspension using Tamiflu capsules. Compounding became necessary in 2009 during a shortage of the drug.

And Genentech just last week reported another shortage of Tamiflu, via the FDA's list of drugs in short supply. The company, which cites increased demand as the cause, said it expects to begin releasing the drug by mid-month.

- here's the announcement
- see the FDA Tamiflu listing