%0 Journal Article
%T Evaluation of Extended Interval Dosing Aminoglycosides in the Morbidly Obese Population
%A Ashley L. Ross
%A Jennifer L. Tharp
%A Gerald R. Hobbs
%A Richard McKnight
%A Aaron Cumpston
%J Advances in Pharmacological Sciences
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/194389
%X Aminoglycoside dosing has been studied in the obese population, typically recommending an adjusted weight utilizing a 40% dosing weight correction factor (IBW + 0.4 ¡Á (TBW¨CIBW)). These studies included limited numbers of morbidly obese patients and were not done in the era of extended interval aminoglycoside dosing. Here, we report a retrospective evaluation of morbidly obese patients receiving gentamicin or tobramycin at our hospital. The objective of this study was to evaluate the accuracy of the commonly recommended adjusted weight for weight-based dosing. There were 31 morbidly obese patients who received gentamicin or tobramycin 5¨C7£¿mg/kg every 24 hours using a 40% dosing weight correction factor. Our institution utilizes 16-hour postdose concentrations to monitor extended interval aminoglycosides. Twenty-two of the 31 patients (71%) achieved an appropriate serum drug concentration. Four patients (13%) were found to be supratherapeutic and 5 patients (16%) subtherapeutic. The only variable that correlated with supratherapeutic levels was older age ( ). Our study helps to validate the current dosing weight correction factor (40%) in the morbidly obese population. We recommend caution when dosing aminoglycosides in morbidly obese patients who are of older age. 1. Background The World Health Organization (WHO) estimated that 500 million people worldwide were obese in 2008 and that number would increase to 700 million by 2015 [1]. In 2011, all 50 states in the United States estimated that 20% or more of their adult population was obese (body mass index ¡Ý 30£¿kg/m2); 12 out of the 50 states estimated that more than 30% of their adult population was in this category [2]. Not only the prevalence of obesity is rapidly increasing, but the weight of obese patients continues to rise with five percent of Americans now being considered morbidly obese (body mass index ¡Ý 40£¿kg/m2) [3]. Several clinical studies, case reports, and review articles have described that pharmacokinetic properties are altered in obese patients compared to ideal body weight (IBW) patients [4¨C15]. There are four main issues that merit discussion when evaluating pharmacokinetic alterations in obesity: absorption, distribution, metabolism, and elimination. The absorption of most drugs is thought to be relatively unaffected by obesity [16]. However, studies in obese patients have shown an altered volume of distribution due to their increased blood flow and cardiac output, changes in protein binding, and organ mass [16, 17]. The metabolism of drugs in this particular population is poorly
%U http://www.hindawi.com/journals/aps/2013/194389/