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Advances in Pharmacological Sciences
Volume 2013 (2013), Article ID 194389, 5 pages
Clinical Study

Evaluation of Extended Interval Dosing Aminoglycosides in the Morbidly Obese Population

1Department of Pharmacy, Jewish Hospital, 200 Abraham Flexner Way, Louisville, KY 40202, USA
2Department of Pharmacy, Johnson City Medical Center, 400 North State of Franklin Road, Johnson City, TN 37604, USA
3Department of Statistics, West Virginia University, P.O. Box 9190, Morgantown, WV 26506, USA
4Department of Pharmacy, West Virginia University Healthcare, 1 Medical Center Drive, Morgantown, WV 26506, USA
5Osborn Hematopoietic Malignancy and Transplantation Program, Mary Babb Randolph Cancer Center, West Virginia University, Morgantown, WV 26506, USA

Received 23 April 2013; Revised 25 July 2013; Accepted 25 July 2013

Academic Editor: Karim A. Alkadhi

Copyright © 2013 Ashley L. Ross et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Aminoglycoside dosing has been studied in the obese population, typically recommending an adjusted weight utilizing a 40% dosing weight correction factor (IBW + 0.4 × (TBW–IBW)). 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 5–7 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.