Objectives: The objectives of this study were to: (1) derive equations for estimating gentamicin clearance (Clgent) and volume of distribution (Vd) based on the local population attending Al-Amiri Hospital, Kuwait; (2) independently evaluate these equations by comparison with other published methods in their predictive ability to estimate Clgent and Vd. Materials and Methods: Clgent and Vd were calculated in 47 patients (group 1) using the Sawchuk-Zaske method. Regression analysis was used to derive a correlation between creatinine clearance (Clcr) and Clgent, Vd and actual body weight (ABW). Based on actual Clgent and Vd values, the predictive ability of the estimated parameters from the regression equations was validated and compared with 4 published methods using mean error (ME), i.e. bias, and mean squared error (MSE) and root mean squared error (RMSE), i.e. precision. All equations were also evaluated in an independent second group (group 2) of 23 patients. Results: The mean ± SD values of Clgent and Vd were 4.0 ± 1.8 l·h–1 and 16.8 ± 6.7 liters, respectively. The derived equations were: Clgent = (0.760) (Clcr) + 1.117 (r = 0.701) and Vd = (0.165) (ABW) + 5.604 (r = 0.532). In comparison to the 4 published methods, the derived equations were less biased (ME = 0.00) and more precise (MSE = 1.68, RMSE = 1.02) in predicting Clgent (p < 0.05), and less biased (ME = –0.01) with no difference in precision (MSE = 36.22, RMSE = 4.59) in predicting Vd (p > 0.05). This precision was confirmed in the second group of 23 patients, where the derived equations were less biased (ME = –0.1) and more precise (MSE = 3.22, RMSE = 1.48) in predicting Clgent (p < 0.05), whilst no difference was found for prediction of Vd (p > 0.05). Conclusion: The equations developed in this study provided a reliable estimation of Clgent and Vd. It is planned to use them at Kuwait Hospitals to help provide more individualized patient dosing information to physicians.

Keywords:
Gentamicin, Pharmacokinetics, Initial dosing parameters, Prediction error
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© 2009 S. Karger AG, Basel
2009
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