Multicenter study of bitolterol and isoproterenol nebulizer solutions in nonsteroid-using patients

Bitolterol mesylate, 1.0 mg, or isoproterenol hydrochloride, 1.5 mg, was administered three times daily for 3 months in a double-blind, multicenter study via closed-port, intermittent-flow, compressor-driven nebulizer system (CPIF) to 182 nonsteroid-using patients with asthma. Mean baseline FEV1 was approximately 60% of predicted normal for both groups. Pulmonary function tests and vital signs were measured before and for up to 8 hours after treatments on test days 1, 30, 60, and 90. Mean maximum increases in FEV1 were 51%, 54%, 52%, and 55% for bitolterol versus 48%, 46%, 50%, and 43% for isoproterenol on these monthly test days. The mean FEV1 response remained greater than 15% over zero time (baseline) for greater than or equal to 8 hours after medication with bitolterol on each of four monthly pulmonary function test days and 2 1/2 to 5 hours for isoproterenol. Median durations of bronchodilator activity for bitolterol were 7.3, 6.5, 6.5, and 6.0 hours versus 4.0, 1.7, 3.7, and 1.9 hours for isoproterenol on the monthly test days. On these test days, 37% to 49% of the patients treated with bitolterol had a duration of action of at least 8 hours compared with 16% to 29% after isoproterenol treatment. The onset of activity was within 5 minutes for both drugs. Bitolterol provided superior bronchodilator activity with fewer adverse effects compared with isoproterenol, and there was no evidence for drug tolerance during this 3-month study.