Identification of children for whom routine monitoring of aminoglycoside serum concentrations is not cost effective

Abstract

On the basis of our clinical impression that aminoglycoside serum concentration measurements did not result in dosage changes in many children with normal renal function, data collected during pharmacokinetic consultations were evaluated to identify pediatric patients for whom routine serum concentration monitoring would not be cost effective. The frequency of peak or trough concentrations outside the desired ranges was related to age and duration of therapy in 88 children with normal renal function who were given recommended doses of gentamicin or tobramycin. Trough concentrations were outside the target range (greater than 2 micrograms/ml) in five of 26 patients who had received more than 10 days of therapy or were older than 18 years of age. In contrast, troughs were less than 2 micrograms/ml and did not significantly increase over the course of therapy in all patients who were younger than 18 years of age and had received less than 10 days of therapy. This latter group represented 36% of all aminoglycoside pharmacokinetic consultation requests to our service. In addition, when infusion technique and sample time were meticulously controlled, peak concentrations were greater than or equal to 4 micrograms/ml in all patients who had received a dose of approximately 2.5 mg/kg. We conclude that routine peak and trough measurements are unnecessary in patients between 3 months and 18 years of age unless duration of therapy extends beyond 10 days, renal function is impaired, there is a clinical need for higher doses or shorter dosing intervals, or a potential nephrotoxin has been administered in the previous 3 months.