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The pharmacokinetics of 1-(35-dihydroxyphenyl)-2-(tert.butylamino)ethanol (terbutaline, Bricanyl) after i.v. and s.c. injection to normal humans and after s.c. and p.o. administration to patients was studied. The kinetic measurements showed that the standard deviations of the respective parameters were not excessively large. Therefore a reasonable production of the behaviour of terbutaline in man is possible. Some important parameters are the biological half-life at 3.6 h (SD = 1.0), the body clearance at 0.26 l/(kg x h) (SD = 0.09), the volume of the reference compartment at 0.47 l/kg (SD = 0.10) and the volume in the steady state at 1.01 l/kg (SD = 0.14). The absolute bioavailability is calculated at 10%.

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.

A method is described for the quantitative analysis of terbutaline in human tissues. Gas chromatography and chemical ionization mass fragmentography are used for selective and sensitive detection. A detection limit of 1.5 ng of the free drug per gram tissue is observed when 0.5 g of the dry tissue is used. No interference from the major metabolite, the sulphate conjugate of terbutaline, is found. Finally the method is applied to the post mortem tissues of two persons who used terbutaline frequently.