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 a nd rectal dosing of SB solution in rabbits, SB and its glucuronide (SB G) in plasma and urine were determined. The bioavailability estimated by the area under the blood concentration-time curve (AUC) of SB from 0 to 9h after oral and rectal administrations were 1.1 +/- 0.5% and 7. 8 +/- 2.2% (mean +/- S.E., n = 5), respectively. Percent of dose excre ted in urine as total SB (SB+ SBG) 10 h after oral and rectal administ rations were 77.3 +/- 3.82% and 9.80 +/- 0.15% (mean +/- S.E., n = 3), respectively, which indicating relatively good oral and poor rectal S B absorption. A partial avoidance of first-pass-effects might contribu te to higher bioavailability after the rectal administration.