Pharmacokinetics of terbutaline after parenteral administration

The basal model-independent pharmacokinetic parameters body clearance (CL), renal clearance (CLR), mean residence time (MRT), and volume of distribution in steady state (Vss) were calculated from concentrations of terbutaline in plasma and amounts in urine after intravenous administration of the drug in 19 healthy men. The data used were from three separate studies. Measurements up to 12 h gave estimated values for CL from 136 mL/min to 340 mL/min, for CLR from 82 mL/min to 192 mL/min, for MRT from 1.5 h to 5.6 h, and for Vss from 24 L to 73 L. In 6 subjects, there were measurements for longer than 24 h that could be used to calculate the parameters. Body clearance was now found to vary between 165 and 270 mL/min. MRT between 7.3 and 11.7 h, and Vss between 83 and 140 L. The evaluations indicate that CL will be overestimated and MRT and Vss underestimated from data only up to 12 h.