Effect of four intravenous infusion methods on tobramycin pharmacokinetics

The influence of four intermittent intravenous infusion methods on the determination of tobramycin pharmacokinetic values and predicted doses was evaluated in 11 healthy adult volunteers. Each subject received tobramycin (as the sulfate salt) 1.5 mg/kg by each of four i.v. infusion methods: (1) minibag via gravity flow (MG), (2) minibag with the secondary infusion tubing inserted below a volumetric pump (MP), (3) metered chamber via volumetric pump (MC), and (4) syringe pump (SP). Infusion rates were initially set to administer each dose over a 30-minute period. Sixteen blood samples were obtained over an eight-hour period before and at various time intervals after each dose and were analyzed for tobramycin content by fluorescence polarization immunoassay. Area under the serum concentration-time curve from time zero to infinity (AUC0-infinity) was calculated by the trapezoidal rule. Serum tobramycin concentration data for each subject were fitted to a biexponential decay model with zero-order input. beta and V beta were calculated from fitted data. One-compartment pharmacokinetic values, elimination rate constant (kappa), apparent volume of distribution (V), and predicted doses to achieve steady-state peak concentrations of 6 micrograms/mL were calculated by the method of Sawchuk and Zaske. There were no significant differences in either beta or kappa among the infusion methods. V beta values (mean +/- S.D.) for the methods were 0.240 +/- 0.025 (MG), 0.257 +/- 0.025 (MP), 0.221 +/- 0.027 (MC), and 0.231 +/- 0.032 (SP) L/kg.(ABSTRACT TRUNCATED AT 250 WORDS)