Theophylline levels and clinical response in asthmatic adults receiving long-term Uniphyl

Serum theophylline levels were measured in response to a single daily dose of Uniphyl in asthmatic adults who had previously received sustained-release theophylline preparations (usually TheoDur). Nine men and 20 women between the ages of 20 and 75 with a one-second forced expiratory volume (FEV₁) of 30 to 75 percent of predicted and with at least 15 percent improvement in FEV₁ following an inhaled beta-adrenergic agonist were enrolled. Patients with coexisting major organ system dysfunction were excluded. Maintenance prednisone in a dosage of 20 mg or less each morning and inhaled corticosteroids were allowed. The five-week study included a baseline week when the usual sustained-release theophylline was continued; theophylline blood levels were determined at six to 10 hours on the fifth day. Patients then switched to an equivalent dose of Uniphyl with single morning dosing. FEV₁ and serum theophylline levels were observed weekly as during the baseline period. Side effects were carefully monitored throughout the study. Concurrent therapy included inhaled beta agonist in 28, oral prednisone in 11, and beclomethasone in one. Serum theophylline levels were remarkably stable during the four Uniphyl weeks and averaged 15 μg/ml. During this time, a small improvement in FEV₁ occurred in weeks 2 and 4 (p <0.05). Only two patients reported substantial side effects—nervousness and slight morning dizziness—which responded to a downward adjustment of Uniphyl dosage. This study indicated that, in asthmatic patients previously receiving twice-daily theophylline therapy, switching to a daily single dose of Uniphyl maintained stable blood levels with a very low incidence of side effects and a modest improvement to FEV₁ at the time of the normal serum peak of theophylline. This study suggests that Uniphyl can replace twice-daily theophylline dosing, which may result in improved patient compliance.