Bambuterol: Uptake and Metabolism in Guinea Pig Isolated Lungs

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Abstract
The lung uptake and biotransformation of 3H-bambuterol, a prodrug to terbutaline, were studied using isolated perfused and ventilated guinea pig lungs. 14C-Sucrose was used as an extracellular marker. The lung uptake of bambuterol was significantly (0.05 ≥P≥ 0.001) higher than that found for sucrose in single-pass perfusion experiments. High-performance liquid chromatographic (HPLC) analysis showed that 95.6 ± 3.6% of the effluent 3H radioactivity was attributable to bambuterol. In recirculating experiments (120 min) the lung biotransformation of 3H-bambuterol (8.5 pmol/ml) was studied. Both oxidative and hydrolytic metabolism took place. The dominating metabolites were hydroxylated bambuterol and the monocarbamate derivative which is a product of hydrolysis of bambuterol. Traces of terbutaline were also formed. The results show that bambuterol has a certain affinity to lung tissue and that the drug is, to some extent, biotransformed in the guinea pig lung.