Long-term oral therapy of asthma with terbutaline and theophylline, alone and combined.

Bronchodilation and side effects of 28 days treatment with either a full therapeutic dose of theophylline slow-release preparation 500 mg twice daily (400-600 mg), a slow-release terbutaline preparation 10 mg twice daily or combinations of the 2 drugs in full or half doses were evaluated in 31 asthmatic outpatients in a double-blind, randomized crossover design. The combination of half doses of the 2 drugs produced slightly better bronchodilation than high-dose, single drug regimen and similar bronchodilation as a high-dose combination. Side effects during half dose combination were less than when theophylline alone or high dose combination treatment were administered. High-dose combination treatment produced slightly more ventricular ectopic beats and supra ventricular ectopic beats, and 3 patients developed cardiac arrhythmias. A combination of half the normally used doses of oral slow-release formulations of terbutaline and theophylline seems superior to a high-dose combination.