Therapeutic equivalence between bambuterol, 10 mg once daily, and terbutaline controlled release, 5 mg twice daily, in mild to moderate asthma.

Bambuterol is the first long-acting oral beta 2-agonist with a 24 h effective duration. In order to investigate the possibility of replacing established treatment modalities with bambuterol once daily, we wanted to compare the bronchodilating and tremorogenic effects of bambuterol, 10 mg once daily, and terbutaline, 5 mg controlled-release (CR) tablets twice daily. The study was of a double-blind, double-dummy, randomized, cross-over design and involved two, two week treatment periods, separated by a one week wash-out period. Peak expiratory flow (PEF) recorded in patients' diaries was the primary efficacy variable. Seventy adult, asthmatic out-patients with mild to moderate asthma were included (forced expiratory volume in one second (FEV1) > or = 50% predicted). After treatment with bambuterol, mean morning and evening PEF (SD) were 347 (122) and 365 (121) l.min-1, respectively and 346 (121) and 365 (122) l.min-1, respectively, after treatment with terbutaline. FEV1 (SD) was 2.21 (0.91) l and 2.27 (0.93) l after bambuterol and terbutaline treatments, respectively. Tremor scores tended to be lower during treatment with bambuterol, although not significantly so. Tremor scores were low, in general. In conclusion, no difference in the bronchodilating effect was demonstrated between bambuterol, 10 mg once daily, and controlled release terbutaline, 5 mg twice daily. A tendency towards less tremor was seen with bambuterol.