Bioavailability assessment of salbutamol sulfate suppositories in human volunteers.

The purpose of this investigation was to evaluate the bioavailability of three salbutamol sulfate suppository formulations. The formulations were; 2 mg salbutamol sulfate in Suppocire NA base containing 6% Eudispert gel (F1), 2mg salbutamol sulfate in Witepsol H15 base containing 3% methyl cellulose gel (F2), and 2 mg salbutamol sulfate in Witepsol W25 base containing 3% methyl cellulose gel (F3). The formulations were administered via rectal route in six healthy male adult volunteers. The bioavailability of the three suppository formulations was compared with the oral bioavailability of salbutamol sulfate 2mg tablets (F4). Six volunteers participated in a four-way crossover study, where each study was separated from the other by an interval of 1 weak. Venous blood samples of 5 ml were taken immediately before dosing and after predetermined time intervals of 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6 and 8 h. The result showed that Cmax +/- S.D. observed were 12.96 +/- 2.11, 14.78 +/- 2.33, 10.02 +/- 1.42 and 11.51 +/- 1.22 ng ml(-1) for F1, F2, F3 and F4, respectively. The Tmax +/- S.D. were found to be 1.91 +/- 0.20, 1.83 +/- 0.26, 2.50 +/- 0.00 and 2.67 +/- 0.24 h for F1, F2, F3 and F4, respectively. AUC +/- S.D. values were 40.25 +/- 1.88, 42.16 +/- 1.55, 28.62 +/- 1.98 and 37.63 +/- 1.44 ng h per ml for F1, F2, F3 and F4, respectively. The relative bioavailabilities of the investigated formulations were 112.04, 106.96 and 76.06 for formula F2, F1 and F3, respectively, when compared with the oral preparation (F4). The finding indicates that the bioavailability of salbutamol sulfate can be enhanced by delivering it rectally with Suppocire NA base containing 6% Eudispert gel or with Witepsol W25 base containing 3% methyl cellulose to match that of oral tablets. Salbutamol sulfate can be rectally administered in patients who are less compliant with the oral administration.