• Terbutaline;
  • ibuterol;
  • lung disposition;
  • rat

Abstract The absorption from the airways, uptake from the vascular compartment and biotransformation of 3H–ibuterol (diisobutyrate ester of terbutaline) and 3H–terbutaline have been studied using isolated perfused and ventilated rat lungs. After endotracheal instillation, ibuterol was more rapidly absorbed than terbutaline (P < 0.01 at 5 and 10 min. after administration) at doses of 55 and 550 nmol/lung. No difference was noted at 5.5 nmol/lung. When the drugs were added to the perfusion medium the calculated lung uptake for ibuterol was about 30 times that for terbutaline. Ibuterol was shown to be rapidly hydrolyzed to terbutaline. No or minor biotransformation of terbutaline was noted.