Bioavailability of propranolol in the dog.

The pharmacokinetics of propranolol in a fasted dog was examined following single oral, intraportal and intravenous doses. Extensive tissue uptake of propranolol occurred after intravenous dosing, the overall distribution volume was 11 liters/kg. Biological half-life was 1.5 hr, but was prolonged after oral and intraportal drug administration. Following oral doses, the absorption efficiency of propranolol as unchanged drug was 71%, while first-pass metabolism accounted for a further loss of 62% prior to its reaching the systemic circulation. Accordingly, the overall oral bioavailability was 27%.