Tamiflu Dosing Problems May Occur for Children Due to Confusing Label

Medical experts and the FDA have expressed concerns that the dosing instructions on Tamiflu oral suspension prescribed for children are so confusing that doctors and patients may have trouble figuring out the proper dosage, potentially resulting in compromised treatment or toxic effects.

The warning was first issued in a letter published in the September 23 issue of the New England Journal of Medicine, which was submitted by several medical professionals. The letter notes that the label for Tamiflu by the pharmacy lists dosage as ¾ of a teaspoon, while the syringe used for administering the medicine orally to young children is marked only in milligrams.

On September 24, the FDA followed up with a public health alert warning about the possibility of Tamiflu dosing problems. The FDA is recommending that prescribers and pharmacists make sure that the dosing instructions are in milliliters and that the dosing dispenser have milliliters on the label as well before filling prescriptions. The FDA said the doses should never be prescribed in teaspoons, due to increased inaccuracy.

Tamiflu (oseltamivir) was approved by the FDA in 1999 for the treatment and prevention of influenza. It is an orally active neuraminidase inhibitor that works by slowing the spread of the flu virus between cells in the body.

The letter published in the New England Journal of Medicine included information about the parents of a six-year old with the flu who had to consult tables in a medical guide issued for prescribers of Tamiflu to find the mathematical formula for translating teaspoons to milliliters. The parents, one of whom was a doctor, finally figured out that ¾ of a tablespoon equaled 45 mg on the Tamiflu oral suspension syringe. However, the authors expressed concern that most parents may not accurately perform the calculations or know how, and may give their children an incorrect dose.

In the health alert, the FDA provides a table with proper dosing instructions for Tamiflu in milliliters, based on body weight.

Tamiflu is often prescribed to children who have been diagnosed with the strain of the H1N1 influenza virus known as “Swine Flu”. The U.S. Centers for Disease Control and Prevention report that while 99.6% of seasonal H1N1 virus are resistant to Tamiflu, only 0.6% of the 2009 pandemic Swine Flu virus has shown to be resistant.