Absolute and Relative Bioavailability of a Slow Release Theophylline Preparation in Asthmatic Children

Abstract

This study was carried out on 14 asthmatic childen aged 7–13 years. They all received three preparations (aminophylline by intravenous infusion, lysine theophyllinate orally in solution and slow release theophylline orally as capsules) in a single dose of 100 mg active ingredient in a crossover design. Plasma theophylline concentrations, determined by a fluorescent polarization immunoassay, were evaluated both by compartmental and non-compartmental analysis. After administration of slow release theophylline, its maximum plasma concentration and the time needed to reach this were (± SD) 3.19 ± 0.63 μg/ml and 8.71 ± 2.30 h, respectively, compared to 4.51 ± 0.94 μg/ml and 1.96 ± 0.85 h, respectively, for the oral normal release solution. Mean absolute and relative percentage bioavailabilities for slow release theophylline in asthmatic children were (± SD) 92.7 ± 23.2% and 83.14 ± 14.69%, respectively. These are similar to the values found with other slow release formulations in paediatric patients.