Specifically in (morbid) obese patients information on optimal dosage of antibiotics is scarce. This is an important problem since the prevalence of obesity is increasing worldwide, and obesity is known to influence different pharmacokinetic parameters such as clearance and distribution volume.

For severe life-threatening infections, vancomycin, gentamicin and tobramycin are important antibiotics, of which the serum concentrations are known to be related to both efficacy and toxicity measures. There are to date no specific guidelines available for clinical practice on how to adjust the dose of these antibiotics in (morbid) obesity. As a consequence, the chances that target concentrations will be rapidly reached in obese patients are small. Therefore, the goal of this study is to characterize the pharmacokinetics of vancomycin, gentamicin and tobramycin in (morbidly) obese patients, ultimately to develop dose guidelines for these drugs that result in a predictable desired exposure with optimal efficacy and minimal toxicity in this special patient population.