Oral bambuterol compared to inhaled salmeterol in patients with partially reversible chronic obstructive pulmonary disease

Objective: There is now good evidence that inhaled salmeterol is an effective agent in chronic obstructive pulmonary disease (COPD),but, at the present time, data on the effects of bambuterol, which is an oral tarbutaline pro-drug, in patients with COPD are scarce. Moreover, no comparative study between bambuterol and salmeterol in patients with chronic obstructive airway disorders has been published. The objective of this research was, consequently, to compare the efficacy and safety of 20 mg oral bambuterol and 50 μg inhaled salmeterol in patients with partially reversible COPD. Methods: The speed and length of bronchodilation with 20 mg bambuterol and 50 μg inhaled salmeterol were compared in 16 patients with partially reversible COPD. The investigation and designed as a double-blind, double-dummy, cross-over, placebo controlled and randomised study. Lung function (FEV₁, FVC) and systemic variables (subjective tremor, heart rate, blood pressure) were monitored prior to the administration of the drug and for 12 h after each agent on 3 non-consecutive days. Results: Inhalation of salmeterol induced a significant (P < 0.05) increase of lung function when compared with placebo. In addition, oral bambuterol elicited good bronchodilation, with its maximum slightly later than for salmeterol. The mean (±SE) AUC_0–12 hs for all patients were 3.134 1 ± 0.553 for salmeterol and 1963 1 ± 0.573 for bambuterol. Both AUC_0–12 h s were significantly greater than for placebo (P < 0.05), but there was no significant difference (P = 0.077) between the salmeterol and bambuterol AUC_0–12 hs. Bambuterol, but not salmeterol, caused tremor in four patients. Moreover, it induced a higher heart rate when compared with salmeterol at each considered time after the administration of the drug; differences after 9 and 12 h  were statistically significant (P < 0.05). Conclusion: Both oral bambuterol and inhaled salmeterol resulted in good bronchodilation in patients with stable COPD. However, bambuterol, but not salmeterol, caused tremor in several subjects and elicited a more pronounced tachycardia. Received: 11 May 1998 / Accepted in revised form: 13 September 1998