Pharmacokinetics of terbutaline after subcutaneous administration

The pharmacokinetics of terbutaline has been studied after subcutaneous adminsitration of a therapeutic dose of 250 microgram in 14 patients. Short absorption half-lives of about 7 min resulted in a fast uptake of the drug. Serum concentrations of terbutaline were measured up to 10 hr after administration, depending on the individual. An open one-compartment model appeared adequate for the mathematical description of the kinetics in most patients. Elimination constants of 0.27 +/- 0.07 hr-1 were observed. The elimination process was biphasic in 5 patients with a mean elimination constant of the second phase of 0.10 +/- 0.04 hr-1. This resulted in a comparatively high concentration of 0.7 ng/ml 10 hr after administration. Regular use of terbutaline did not influence the pharmacokinetic data in a significant way.