Comparison of Tobramycin Pharmacokinetics After Administration by Cris and a Traditional Intravenous Piggyback Infusion

Objective: To compare the administration pharmacokinetics of a 30-minute intravenous piggyback (ivpb) infusion of tobramycin with those of controlled-release infusion system (CRIS) using a 20-mL vial at rates of 60 and 120 mL/h. Design: Randomized, controlled, crossover, prospective, open-label trial. Setting: Medical college-affiliated hospital. Participants: Eight healthy volunteer men between the ages of 22 and 24 years weighing between 60 and 90 kg. Interventions: Volunteers received, in random order, tobramycin sulfate 2 mg/kg iv on 3 occasions separated by 1 week. The drug was administered using a 50-mL ivpb infusion at 100 mL/h for 30 minutes, and with the CRIS using a 20-mL vial with flow rates of 60 mL/h for 1 hour (slow) and 120 mL/h for 1 hour (fast). Main Outcome Measures: Primary endpoints were area under the time–concentration curve (AUC), time to reach maximum concentration (tmax), and maximum concentration (Cmax). Secondary endpoints were elimination rate constant (ke), clearance (Cl), and half-life (t1/2). Results: Six volunteers successfully completed the trial. The tmax values observed following fast CRIS and ivpb were 28 ± 8 and 32 ± 4 minutes, respectively, and not significantly different from each other. Both occurred significantly earlier than the tmax associated with slow CRIS (44 ± 7 min). The Cmax values observed following ivpb (11.2 ± 1.5 mg/L) and slow CRIS (10.9 ± 0.9 mg/L) administration were not significantly different from each other, but both were significantly lower than that of fast CRIS (13.4 ± 1.5 mg/L). The AUCs of slow and fast CRIS were 29.8 ± 4.8 and 31.2 ± 3.8 mg/L•h, respectively, and were not significantly different from each other. The AUC of fast CRIS was significantly greater than that observed with ivpb (27.4 ± 4.3 mg/L•h). No significant difference in ke (fast CRIS 0.32 ± 0.03 h-1; slow CRIS 0.33 ± 0.04 h-1; ivpb 0.34 ± 0.0 h-1) was observed among any of the methods. Conclusions: CRIS administration of tobramycin resulted in higher AUCs than did ivpb administration. Compared with ivpb, fast CRIS resulted in a higher Cmax, but the tmax values of fast CRIS and ivpb administration were not statistically different. Compared with ivpb, slow CRIS resulted in a more delayed tmax, but the Cmax values of slow CRIS and ivpb were not statistically different.