Letter Warns About Tricky Dosing With Liquid Tamiflu for Kids

THURSDAY Sept. 24, 2009 -- Doctors warn that parents across the country could give the wrong dose of Tamiflu to their children as treatment for the H1N1 swine flu because the dosing instructions don't always coincide with the measurement markings on the syringe that comes with the liquid medication.

The warning letter, penned by scientists from Northwestern University Feinberg School of Medicine in Chicago, Emory University in Atlanta and Weill Cornell School of Medicine in New York City and published online Wednesday in the New England Journal of Medicine, also urges doctors and pharmacists to be on the lookout for this potential dosing mismatch and to help parents figure out exactly how much Tamiflu to give their child.

The authors cite a case that they say is probably happening all over the United States: The parents of a 6-year-old girl diagnosed with the H1N1 virus received a prescription for Tamiflu Oral Suspension that told them to give her three-fourths of a teaspoon of the medicine two times a day. However, the dosing syringe inside the box was marked in milligrams. The confused parents, both of whom are health professionals, had to figure out how to convert the measurement, something most parents would find too daunting to do.

"It's an egregious error that there is a conflict in the prescription labeling instructions and the dosage device that comes in the exact same box. It's incredibly confusing to parents," letter co-author Michael Wolf, an associate professor of medicine and learning sciences at Northwestern University Feinberg School of Medicine, said in a news release from the university. "Tamiflu is one of the main courses of treatment right now for H1N1, and it is being widely used among children, even infants."

The letter's authors recommend that all pharmacies and physicians be instructed to ensure that the prescription label instructions for use are in the same dosing units as those on the measurement device.

"Parents being prescribed Tamiflu for their children need to make sure they understand exactly how to take it at the time they pick it up at the pharmacy," lead letter author Dr. Ruth Parker, a professor of medicine at Emory, said in the release.

Wolf warned that an overdose could be toxic, and an underdose could be ineffective.

And even more complex calculations might be necessary now that the U.S. Food and Drug Administration has approved Tamiflu for off-label use among children under the age of 1, because the syringe doesn't include small enough measuring increments for these youngest patients.

"We need to have a better system for ensuring there are standardized directions for administering drugs to children," letter co-author Dr. Alastair Wood, a professor of medicine and pharmacology at the Weill Cornell School of Medicine in New York City, said in the news release. "We need to move to a system where all doses are given in the same units, preferably milliliters."

Meanwhile, a report released Thursday supports recent U.S. Centers for Disease Control and Prevention recommendations not to use negative rapid test results for management of patients that may be infected with the pandemic swine flu virus.

Researchers in Connecticut assessed the performance of the rapid influenza diagnostic test (RIDT) used during outbreaks of pandemic influenza A (H1N1) at two schools in Greenwich in May 2009. Of the 63 people tested at Greenwich Hospital, infection was confirmed in 49 patients.

The results of the RIDT were compared with the reverse transcription--polymerase chain reaction assay. A low sensitivity of 47 percent was found for the rapid test. This poor performance couldn't be explained by the clinical features of the patients or by the timing of the specimen collection, said Dr. James R. Sabetta, of the Greenwich Department of Health and the Connecticut Department of Public Health, and colleagues.

While a positive rapid test for influenza is helpful, a negative test doesn't rule out pandemic swine flu, the researchers said.

The report appears in the Sept. 25 issue of the Morbidity and Mortality Weekly Report, published by the CDC.

More information

The CDC has more about H1N1 flu.

Posted: September 2009


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