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Dosing Instructions for Kids May Cause Serious Errors

September 24, 2009 | by Marla Paul
CHICAGO --- Parents giving their children Tamiflu for the H1N1 virus could potentially give the wrong dose because the prescription instructions on the label may not match the  markings on the syringe included with the drug inside the box.

A letter alerting medical and public health officials to the problem was published in Online First by the New England Journal of Medicine (NEJM) Wednesday afternoon. The letter authors are scientists from Northwestern University Feinberg School of Medicine, Emory University and Weil Cornell School of Medicine.  

In one case, which the authors say is likely being played out repeatedly across the country, the parents of a 6-year-old girl diagnosed with the H1N1 virus received a prescription for Tamiflu Oral Suspension that instructed them to administer three-fourths of a teaspoon of the medication twice daily. But the prepackaged dosing syringe inside the box was marked with milligram measurements. The confused parents had to try to figure out how to convert the partial teaspoon measurement to the mass units of milligrams - a task that many parents will not be able to do.

Using a spoon from the kitchen to measure the medicine does not provide an accurate dose and is a practice warned against by the American Academy of Pediatrics.  

"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," said Michael Wolf, a coauthor of the NEJM letter and associate professor of medicine and learning sciences at Northwestern University Feinberg School of Medicine. "Tamiflu is one of the main courses of treatment right now for H1N1, and it is being widely used among children, even infants."

Wolf and the other 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," advised Ruth Parker, M.D., the lead author of the letter and a professor of medicine at Emory University School of Medicine. She noted that this type of misalignment between the prescription label and the dosing device also occurs in other pediatric medicines.

Wolf warned that the misaligned instructions on the pharmacy label and the dosing device could result in an overdose or an underdose.

"If you give too little, you risk making the treatment less effective. If you overdose, there may be a risk of toxicity to the patient," said Wolf, who along with doctors Parker and Alastair Wood, the senior author of the letter, are leading national efforts to improve the quality of drug labeling and consumer medication information.

Even more complex dosing and measurement calculations will be required now that Tamiflu has now been authorized by the FDA for off-label use among children under 1 year of age. The syringe in the Tamiflu package doesn't include small enough increments for these infants.

The mother of the 6-year-old girl who had H1N1 happens to be Kara Jacobson, a letter coauthor and senior research associate at the Rollins School of Public Health of Emory University. Jacobson and her husband, an internist, had to do a Google search and a complex mathematical equation to figure out the correct dose -- 45 milligrams -- for their child. It took 30 minutes, she said, and they are both health professionals. Most families would not be able to figure it out.

"We need to have a better system for ensuring there are standardized directions for administering drugs to children," said Alastair Wood, M.D., professor of medicine and of pharmacology at the Weil Cornell School of Medicine and managing director of Symphony Capital LLC, an investment firm in New York.

"We need to move to a system where all doses are given in the same units, preferably milliliters," Wood said. "But, if we are going to use a teaspoon for historical reasons, we need to use that measurement in the doctor's prescription and the instructions on the label and provide a dispensing device that matches. Parents cannot be expected to transpose from one system of units to another."

The researchers also recommend that all dosing devices should be labeled with volume units, such as milliliters or a teaspoon, and not with weight units like milligrams. "It doesn't even make sense," Parker said. "It's a volume measurement. Put a volume marking on it."
Topics: Research