January 9, 2013
Tamiflu Approved for Use in Infants Older Than 2 Weeks

Washington, D.C.—Pharmacists have a critical role to play in making sure dosages are correct for oseltamivir, now approved for use in infants as young as 2 weeks old who have shown symptoms of influenza for no more than 2 days.

In December, the FDA expanded the approved use of oseltamivir, marketed as Tamiflu, to most children less than a year old. FDA cautions, however, that the safety and efficacy of Tamiflu has not been established in newborns younger than 2 weeks old and that the drug is not approved to prevent flu infection in children younger than a year.

In 1999, Tamiflu was approved for prevention of flu in adults and to treat those with new onset of flu symptoms. It was subsequently approved for prevention in children ages 1 year and older who have shown symptoms of flu for no longer than 2 days, as well as for prevention.

The dosing regimen for patients 1 year and older is fixed based on weight categories, but dosages for children younger than 1 year must be calculated for each patient, based on their exact weight, according to the FDA. Those children should receive 3 milligrams per kilogram twice daily for 5 days, the agency said.

That will require pharmacists to provide a different dispenser than what is currently co-packaged with Tamiflu.

“Pharmacists must provide the proper dispenser when filling a prescription so parents can measure and administer the correct dose to their children,” said Edward Cox, MD, MPH, director of the Office of Antimicrobial Products in the FDA's Center for Drug Evaluation and Research. “Parents and pediatricians must make sure children receive only the amount of Tamiflu appropriate for their weight.”

Tamiflu is the first and only product approved to treat flu infection in children younger than 1 year old. That is especially important because the age cohort is so vulnerable. The CDC points out that children younger than 2 years are at higher risk for developing complications from the flu, with the highest rates of hospitalization in those less than 6 months of age.

To determine whether the use of Tamiflu should be expanded to infants, the FDA used extrapolated data from previous study results in adults and older children as well as safety and pharmacokinetic studies sponsored by the National Institutes of Health and Roche Group, Tamiflu’s manufacturer.

A law passed in 2003 allows the FDA to extrapolate efficacy from previous study results in adults and older children, if the illness being studied and the effects of the drug are sufficiently similar in adult and pediatric patients.

Results from two safety studies with 135 pediatric patients—almost all with confirmed flu —showed the safety profile in children younger than 1 year was consistent with the established safety profile of adults and older children. The most common side effects reported with Tamiflu use in this age group were vomiting and diarrhea.

The FDA noted that, although not seen in the new studies, rare cases of severe rash, skin reactions, hallucinations, delirium, and abnormal behavior have been reported with Tamiflu.

In terms of prevention, Tamiflu should not be substituted for an annual influenza vaccine in any age group, the agency added.

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