Miriam del C. Carrasco-Portugal, Adrian Martinez Talavera, Lina M. Barranco-Gardu?o, Ariadna Cervantes- Nevarez, Juan C. Neri, Gilberto Casta?eda-Hern?ndez and Francisco J. Flores-Murrieta
Oseltamivir is a neuraminidase inhibitor that is very eff ective in the treatment of infl uenza. During 2009 pandemia, this drug was widely used and empirically, obese patients received twice of the recommended dose, assuming that plasma levels may be reduced in this kind of patients. In order to establish if this practice was adequate, we decided to compare the oral pharmacokinetics of oseltamivir phosphate, by measuring oseltamivir carboxylate (the active metabolite), in obese and non- obese volunteers. Th irteen obese and --- non-obese volunteers were enrolled in this study that was approved by the Institutional Research and Ethics Committees and gave written informed consent for participation. Aft er an overnight fast, non-obese subjects received an oral 75 mg dose of oseltamivir phosphate, whereas, obese patients received 75, 150 and 300 mg in three diff erent sessions under a crossover design. Plasma samples were obtained at selected times during --- h and stored frozen until analysis by high-performance liquid chromatography with fl uorescence detection. Pharmacokinetic parameters were obtained by non-compartmental analysis and compared by analysis of variance. Cmax, AUC increased linearly with the administered doses in obese patients, whereas, no statistically signifi cant changes in t1/2 and tmax were observed. Comparison of pharmacokinetic parameters aft er administration of 75 mg in obese and non-obese patients indicated that no diff erence in pharmacokinetics of this drug is observed and therefore, no adjust of dosage regimen based on body weight is required.