Comparison of aminophylline and theophylline sustained-release formulations by their bioavailability and steady-state serum levels.

: The absolute bioavailability of a new aminophylline sustained-release formulation (BY108) was determined. A crossover study was performed with drug intake under fasting conditions and after a standardized breakfast in order to investigate the effect of food on the absorption process. In addition, steady-state theophylline serum levels obtained after administering the new aminophylline formulation twice daily (corresponding to 386 mg anhydrous theophylline twice daily) were compared in a crossover study with those obtained from comparable doses of a commercially available theophylline sustained-release preparation (Theo-Dur, 400 mg anhydrous theophylline twice daily). Bioavailability of BY 108 was complete in reference to both the intravenous standard and Theo-Dur. The tolerance of BY 108 parallelled that of Theo-Dur and was good, considering the relatively high average dose of 10.4 mg/kg/day.