Sustained-release theophylline preparations in asthmatic children. A short-term comparison of two products and the relationship of serum theophylline levels and pulmonary function changes.

In a four-week study, 20 children with chronic asthma were treated in a randomized, double-blind, crossover manner with two sustained-release theophylline preparations (Theo-Dur and Uniphyl) to compare their drug concentrations and clinical efficacy. In addition, the effects of serum theophylline concentration on results of pulmonary function tests (PFTs) were evaluated. Twelve-hour doses (to achieve serum concentrations between 10 and 20 mg/L) of each drug were given for two weeks. Diaries of asthma symptoms and peak flows were kept daily. After 14 days of each treatment, children returned for measurement of theophylline levels and PFTs over a 12-hour period. The two drugs were equally effective in clinically controlling asthma over the two weeks of treatment. Serum theophylline levels obtained over the 12-hour dosing periods were not significantly different. Uniphyl provided less (but not significantly) deviation between peak and trough levels. Analysis of individual patient data did not reveal a predictable relationship between serum theophylline concentrations and results of PFTs.