Riesgo de confusión al dosificar la suspensión de Tamiflu oral en niños

Al Editor
La comunidad médica debería hacer tomar conciencia del peligro potencial de los errores en las dosis de la suspensión oral de Tamiflu (osetalmivir) prescritas a niños, como se ilustra en el caso presentado a continuación
Después del diagnóstico de influenza H1N1, un niño de 6 años recibió una prescripción para la suspensión oral de Tamiflu (Osetalmivir) (12 mg por mililitro) a una dosis de ¾ de cucharadita PO BID. Sin embargo, los padres, uno un médico de atención primaria y el otro, uno de los autores, tuvieron grandes dificultades para determinar la dosis correcta para su hijo. El frasco de medicamento estaba acompañado de una jeringuilla preempacada con marcas en los 30, 45 y 60 mg.. La etiqueta pegada por la farmacia especificaba las dosis en unidades volumétricas (“3/4 de cucharadita”) pero la jeringuilla solo mostraba marcas en unidades de peso (miligramos). A pesar de las instrucciones diferentes, los padres fueron capaces, eventualmente, de determinar la dosis correcta con la ayuda de una de las 10 tablas administradas en el folleto explicativo del envase dirigidas a los médicos, no a los padres, quienes resolvieron la siguiente ecuación para tratar de hallar el equivalente en mgs. de la dosis indicada de ¾ de cucharadita: 5ml (volumen de una cucharadita x 0.75 x 12 mg/ml de la suspensión de Tamiflu, equivalían a 45mg en la jeringuilla.

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 prepackage dosing syringe are misaligned. Thus, there is a high chance for dosing errors, compromised treatment, or toxic effects. Even more complex dosing and measurement calculations1 will be required under the Emergency Use Authorization,2 which has extended the use of oseltamivir to children under the age of 1 year.
Unless immediate steps are taken to improve the prescribing instructions for this drug in children, its safe use will be compromised. We recommend that all pharmacies be instructed to ensure that the label instructions for use are in the same dosing units as those on the measurement device dispensed with oseltamivir. For instance, in the present case, the instructions could have said, “fill the attached syringe to the level marked 45 mg and administer this amount twice a day for 5 days.” If a prescription specifies the dose in teaspoons, only a syringe calibrated in fractions of a teaspoon should be dispensed and the instructions adjusted accordingly; if a prescription specifies the dose in milliliters, only a syringe calibrated in milliliters should be used. In addition, the Consumer Medication Information must be improved and the public alerted to the potential for oseltamivir dosing errors. In the future, all measuring devices for use in children should be marked with volumetric doses (milliliters or teaspoons).

Ruth M. Parker, M.D.
Emory School of Medicine
Atlanta, GA

Michael S. Wolf, Ph.D., M.P.H.
Feinberg School of Medicine
Chicago, IL

Kara L. Jacobson, M.P.H.
Emory School of Medicine
Atlanta, GA

Alastair J.J. Wood, M.D.
Symphony Capital
New York, NY
alastair@symphonycapital.com
Dr. Wolf reports receiving consulting fees from Abbott and Pfizer and grant support from McNeil Pharmaceuticals, and Dr. Wood reports being a partner and investor in Symphony Capital, serving as a director of Oxigene Pharmaceuticals, and receiving consulting fees from International Reinsurance companies. No other potential conflict of interest relevant to this letter was reported.
This letter (10.1056/NEJMc0908840) was published on September 23, 2009, at NEJM.org.