Systemic background

Owing to its rapid bactericidal activity and rela-tively low levels of resistance in most pathogens, gentamicin remains a popular drug in our hospi-tal for suspected serious gram-negative infections, particularly as empirical therapy in combination with a broad-spectrum beta-lactam antibiotic. There are a number of different methods availa-ble for gentamicin therapeutic drug monitoring (TDM), including population-based, linear regression and Bayesian methods. Our current hospital guidelines recommend a population-based nomogram with a single gentamicin con-centration required to be taken between 6 and 14 hours postdose [Begg and Barclay, 1995]. This method is only applicable to patients <65 years with an estimated glomerular filtration rate (eGFR)>60 ml/min and, therefore, is not ideal for many hospital patients. TDM is performed notoriously poorly in many clinical settings [Leong et al. 2006], but it remains uncertain whether suboptimal monitoring in adults adversely impacts on hard clinical outcomes. Indeed, it has been proposed that lower doses may be effective, making toxicity less likely with less need for monitoring [Begg et al. 2001]. The need for TDM, particularly in patients with uncomplicated infections and normal renal func-tion, has been questioned [Christensen et al