Economic impact of aminoglycoside toxicity and its prevention through therapeutic drug monitoring.

Therapeutic drug monitoring (TDM) of aminoglycoside antibacterials with the goal of minimising toxicity and maximising effectiveness has become routine. Successful management of serious infections requires the ability to achieve therapeutic peak concentrations, while maintaining low trough concentrations will assist in avoiding nephrotoxicity. Reported nephrotoxicity rates range from 1.7 to 58% and depend on the definition used, the patient group studied, concomitant drug therapy used and whether TDM services have been provided. TDM services have been shown to reduce aminoglycoside nephrotoxicity. The costs of providing TDM averages $US301.87 (1997 values) per patient and the cost for each use of nephrotoxicity is estimated at $US4583 (1997 values). In order for the costs of providing a TDM service to 100 patients ($US30,187) to be offset by cost savings due to decreasing nephrotoxicity, the service would need to be able to reduce nephrotoxicity by 6.6%, resulting in a saving of $US30,248. The ability to achieve this saving is dependent on the characteristics of the population in which aminoglycoside therapy is used. In populations where high rates of nephrotoxicity (e.g. > 15%) would be expected, TDM services are cost justified. In populations where nephrotoxicity is low (e.g. < 5%), TDM service is not justified for this purpose. In order to provide a cost-efficient approach to TDM, resources should be focused on providing service to high risk patient groups.