Plasma concentrations of salbutamol after an oral slow-release preparation

Studies were carried out to investigate the plasma concentrations of salbutamol after administration of a slow-release formulation (8 mg) compared with those after 1 and after 2 standard 4 mg tablets. In the first study, 9 subjects received, at random, either the slow-release tablet or a single standard tablet. Blood samples were taken and histamine challenge tests were carried out before and at fixed time intervals after drug administration. The procedures were repeated after an interval of at least 5 days with the alternative treatment. In the second study, plasma concentrations were measured in 5 of the subjects before and after taking 2 standard 4 mg tablets. The results showed that there was slower attainment of peak plasma concentrations after the slow-release formulation compared to those after one 4 mg and two 4 mg standard tablets. In addition, the 8 mg slow-release formulation produced lower peak plasma concentrations than did two 4 mg standard tablets. Protection against a bronchoconstricting histamine challenge lasted at least twice as long after the slow-release compared with after a single 4 mg standard tablet.