The CDC and some physicians are warning pharmacies and parents about potentially confusing dosage information distributed with the flu drug oseltamivir (Tamiflu).
The prepackaged syringe that comes with the drug is graded in milligrams, but instructions given to consumers may specify doses in milliliters or teaspoons, according to an update posted yesterday to CDC's formal recommendations on antiviral drug use for influenza.
Much the same point was made, but more forcefully, by three physicians and a public health specialist in a letter published online today in the New England Journal of Medicine.
"The medical community should be made aware of the serious potential for dosing errors in children," they wrote.
The NEJM authors, led by Ruth M. Parker, MD, of Emory University in Atlanta, reported on a six-year-old with the 2009 H1N1 flu who was prescribed oseltamivir.
The label attached by the pharmacy told the parents to give three-quarters of a teaspoon to the child. But the authors said the parents -- both health professionals, one of whom helped write the NEJM letter (but was not named) -- had trouble figuring out a conversion to milligrams, which they needed to use the prepackaged syringe.
They eventually found the needed information in the part of the package insert intended for prescribers, not parents.
Parker and colleagues wrote, "Specifically, they solved the following equation for the milligram equivalent of the 3/4-tsp dose: 5 ml (volume of a teaspoon) x 0.75 x 12 mg per milliliter Tamiflu suspension = 45 mg on the syringe."
"Most families and caregivers would not be able to identify or perform the cumbersome calculations required to administer Tamiflu safely to children, because the instructions on the pharmacy label, on the manufacturer's printed label, and in the accompanying Consumer Medication Information and the prepackaged dosing syringe are misaligned," they asserted.
Howard Markel, MD, a University of Michigan pediatrician, said the problem went beyond oseltamivir. "This is actually a big issue with many liquid medications," he wrote in an e-mail. "Most of us become confused when confronted with number of fluid cc's versus teaspoon amounts, etc."
Parker and colleagues noted that dosing calculations for oseltamivir are even more complex when the drug is administered to infants, now permitted under the government's emergency use authorization.
They said pharmacies should always give dosing instructions in the same units used on the dosing device that comes with the drug.
The CDC's updated recommendations included similar language.
When dispensing oseltamivir, the agency said, "pharmacists should ensure the units of measure on the prescription instructions match the dosing device. If prescription instructions specify administration using milliliters (mL) or teaspoons (tsp), then the device included in the Tamiflu product package should be removed and replaced with an appropriate measuring device, such as an oral syringe if the prescribed dose is in milliliters."
When the drug is intended for children younger than one, the CDC added, a syringe graded in milliliters should always be provided, along with clear instructions to caregivers.
This article was developed in collaboration with ABC News.