Controversies in antimicrobial therapy: pitfalls in monitoring aminoglycoside therapy

Efficacy, safety, and cost factors related to aminoglycoside therapy, which is the treatment of choice for mixed infections of the skin, respiratory tract, and abdominal cavity, are reviewed. The cost of therapy must include all measurable costs of drug preparation, administration, monitoring, and potential toxicity or treatment failure. These costs are often difficult to quantify, as are potential differences in efficacy. Aminoglycosides are usually given by injection and are excreted unchanged by the kidneys. They are concentrated in the renal cortex, leading some investigators to assess the correlation of this uptake with renal toxicity. An increase in serum aminoglycoside concentrations serves as a retrospective, nonspecific marker of the renal toxicity that occurs in up to 35% of patients receiving these drugs. Pharmacokinetic monitoring of aminoglycoside therapy is used to assure therapeutic drug concentrations. Blood samples for aminoglycoside assays must be drawn, stored, separated, and assayed correctly, and the timing and labeling of the sample is of utmost importance. Nomograms and pharmacokinetic models, which can be used with computers and hand-held calculators, are useful for predicting initial doses and modifying subsequent doses. Aminoglycoside therapy is important in selected patients, but the comparative efficacy and safety of these drugs remains insufficiently assessed. Pharmacokinetic monitoring is helpful in assuring safe and effective dosing of aminoglycosides.