Single dose and steady-state pharmacokinetics of 4 mg and 8 mg oral salbutamol controlled-release in patients with bronchial asthma

Summary Fifteen patients with asthma were given salbutamol controlled-release (SCR) 4 mg or 8 mg twice daily for seven days, in a randomised double-blind cross-over design. Plasma salbutamol levels were measured after the first and fifteenth doses for a 12 h period following drug ingestion.At steady-state the geometric mean values for C_max were 8.2 ng/ml for 4 mg, and 16.1 ng/ml for 8 mg. Median t_max values were 300 and 240 min respectively. The geometric mean AUC (0–12) were 4507 ng·min·ml^–1 and 8980 ng·min/ml. Peak to trough fluctuation ratios were 0.577 and 0.572.There were no significant differences between 4 mg or 8 mg formulations, for any of the parameters measured, after appropriate corrections for dose. The concentration-time profiles at steady-state showed little fluctuation in plasma salbutamol levels over the twelve hour dosing interval. These results show that 4 mg and 8 mg formulations of SCR provide smooth plasma profiles at steady-state with a twice daily dosing regime.Part of this paper has been presented in abstract form to the British Thoracic Society, Newcastle, July 1988