The Metabolism of Terbutaline in Man

Abstract

1. The metabolism of terbutaline has been investigated in man after oral, intravenous and subcutaneous administration of the tritium-labelled drug. 2. Serum levels and excretion rates were followed for 3–4 days after administration by the three different routes. After oral administration, one-third to one-half of the dose is excreted in the urine whereas after intravenous and subcutaneous administration >90% is eliminated by this route. The remainder is recovered in the faeces. 3. A method for determination of [³H]terbutaline using ion pair extraction has been developed. A quantitative separation of unchanged drug from its metabolite is achieved in the range 1–250 ng/ml urine or serum. 4. After administration of terbutaline by any of the three routes, high voltage electrophoresis and paper chromatography reveal the presence of only one metabolite. Hydrolysis of urine with β-glucuronidase and/or sulphatase indicates that the major metabolite is a sulphate conjugate of terbutaline.