[Comparison of bioavailability of salbutamol between oral and rectal administration in rabbits]

In order to obtain a basic knowledge for developing the rectal dosage form of salbutamol (SB), a comparison of the bioavailability was made between oral and rectal administrations. After the intravenous, oral and rectal dosing of SB solution in rabbits, SB and its glucuronide (SBG) in plasma and urine were determined. The bioavailability estimated by the area under the blood concentration-time curve (AUC) of SB from 0 to 9 h after oral and rectal administrations were 1.1 +/- 0.5% and 7.8 +/- 2.2% (mean +/- S. E., n = 5), respectively. Percent of dose excreted in urine as total SB (SB+SBG) 10 h after oral and rectal administrations were 77.3 +/- 3.82% and 9.80 +/- 0.15% (mean +/- S. E., n = 3), respectively, which indicating relatively good oral and poor rectal SB absorption. A partial avoidance of first-pass-effects might contribute to higher bioavailability after the rectal administration.