MULTICENTER QUALITY-CONTROL STUDY OF AMIKACIN ASSAY FOR MONITORING ONCE-DAILY DOSING REGIMENS

During once-daily dosing regimens of aminoglycosides, administration o f large single doses results in high peak levels and low 24-h trough l evels. However, commercial assays for monitoring aminoglycoside levels are designed to cover the smaller range of serum concentrations usual ly observed during multiple daily dosing regimens. The study assessed (a) the range of serum concentrations during once-daily dosing of amik acin and (b) the performance of a widely used assay system for measuri ng concentrations within this range. A total of 42 dosing intervals fr om eight patients receiving a once-daily regimen of amikacin (20 mg/kg ) were monitored. Median (and range) of peak, 8- and 24-h trough level s were 61 (25-89), 5.9 (2.2-19), and 1.3 (<0.8-6.2) mg/L, respectively . The accuracy of a fluorescence polarization immunoassay for measurin g concentrations of amikacin during once-daily dosing regimens was ass essed in an international multicenter study. The performance of the as say was excellent for peak and 8-h concentrations; median deviations f rom the target concentrations were <5%. The majority of the trough lev els (26 of 42) measured in patients during once-daily treatment were w ithin the range of 1-2 mg/L and could also be determined with an accur acy sufficient for clinical monitoring (median deviations 14%).