[Theophyllines of 12- and 24-hour sustained-release. Comparative study]

To compare 24-h and 12-h delayed-release theophylline in asthmatic patients, in terms of clinical stability and respiratory function, side effects and required dose, clinical tolerance and plasma concentrations. Patients with bronchial asthma in stable phase taking theophylline every 12 h were selected. Each patient received 12-h (treatment A) and 24-h (treatment B) theophylline formulas in a prospective, cross-over study with paired data for periods of 15 days. We evaluated theophylline doses, blood levels, clinical course, lung function and side effects. Twenty patients were enrolled. No significant differences between the two treatments were observed in mean dose of theophylline per kg body weight required to obtain therapeutic plasma concentrations (treatment A: 9.36 +/- 1.88 mg/kg/day; treatment B: 9.6 +/- 1.7 mg/kg/day). Mean blood level just before administration of a the next dose was lower with the 24-h formula, but still within therapeutic margins (treatment A: 7.31 +/- 2.27 micrograms/ml; treatment B: 10.66 +/- 2.86 micrograms/ml; p = 0.002). There were no differences in side effects after the adjustment period or in FEV1 after each treatment period. Peak expiratory flow remained stable during the study. The 24-h delayed release theophylline formula was similar to the 12-h formula in dose required by asthmatic patients and in therapeutic plasma concentrations throughout the day.