Sustained-release theophylline. Pharmacokinetic and therapeutic comparison of two preparations.

The serum theophylline concentration profiles and clinical efficacy of two sustained-release theophylline tablets (Quibron-T/SR and Theo-Dur) were compared in 13 asthmatic children requiring continuous theophylline therapy. Quibron-T/SR and Theo-Dur, administered every 12 hours in the same dose for one week, were evaluated in a multiple-dose randomized crossover study. At the end of each week, serial serum theophylline concentrations were measured and spirometry and body plethysmography were performed. No significant differences between treatments were found in bioavailability, adverse effects, clinical symptom scores, or pulmonary function in spite of the fact that Quibron-T/SR and Theo-Dur produced significantly different serum theophylline concentration profiles as measured by a mean percent of fluctuation in serum theophylline levels of 143 for Quibron-T/SR and 65.7 for Theo-Dur. Over the short term of the study the pharmacokinetic differences did not produce significant differences in clinical efficacy.