AMINOGLYCOSIDE DOSING WEIGHT CORRECTION FACTORS FOR PATIENTS OF VARIOUS BODY SIZES

Prior investigations have suggested the use of a dosing weight correct ion factor of ideal body weight (IBW) plus 40% excess body weight (EBW , where EBW = total body weight [TBW] - IBW) to determine the weight t o use for aminoglycoside dosing in morbidly obese (TBW/IBW ratio, >2) patients. Little data are available to provide dosing information for underweight or moderately obese patients, We investigated aminoglycosi de pharmacokinetics in 1,708 patients receiving gentamicin and tobramy cin. Patients were stratified into underaverage-weight or overweight w eight categories based on both TBW/IBW ratio and body mass index (weig ht/height(2) ratio), which has been shown to correlate,vith physiologi c estimates of body fat, Regression analyses revealed that the TBW/IBW ratio predicts the volume of distribution, Dosing weight correction f actors to give equivalent predicted peak aminoglycoside concentrations with a 2-mg/kg loading dose are 1.13 times the TBW for underweight pa tients and 0.43 times the EBW plus IBW for overweight patients. There were no large differences between the dosing weight correction factors derived from IBW- and body mass index-based classification systems. T hese data generate useful aminoglycoside dosing weight equations for b oth underweight and overweight patients.