Sustained-release theophylline for treatment of asthma in preschool children.

Theo-Dur, a sustained-release theophylline formulation, was administered every 12 hours for three months to ten asthmatic children aged 3 to 7 years, with no evidence of adverse reaction or tolerance. There was significant temporal variation in serum theophylline concentrations. The mean difference between the peak and trough concentrations was 6.5 micrograms/mL (range, 3 to 14 micrograms/mL) in a 12-hour period. Serum theophylline concentrations correlated well with pulmonary function test results. Nine or more hours after a Theo-Dur dose, some children needed additional bronchodilator treatment and had impairment of pulmonary function. We recommend that children aged 7 years or younger who are given Theo-Dur have monitoring of predose serum theophylline concentrations, symptoms, and signs, as many will require a dose frequency greater than every 12 hours.