EFFECTS OF FORMOTEROL, SALMETEROL OR OXITROPIUM BROMIDE ON AIRWAY RESPONSES TO SALBUTAMOL IN COPD

We examined whether a pretreatment with formoterol, oxitropium bromide , or salmeterol might modify the dose-response curves to inhaled salbu tamol in patients with stable and partially reversible chronic obstruc tive pulmonary disease (COPD). Sixteen outpatients with partially reve rsible, stable COPD received 24 mu g formoterol, 50 mu g salmeterol, 2 00 mu g oxitropium bromide, or placebo on four non consecutive days. S pirometric testing was performed immediately before inhalation of trea tment and after 2 h. A dose-response curve tee inhaled salbutamol was then constructed using doses of 100, 100, 200 mu g and 400 mu g - that is, a total cumulative dose of 800 mu g. Dose increments were given a t 20 min intervals with measurements being made 15 min after each dose . Formoterol, salmeterol, or oxitropium bromide elicited a significant increase in forced expiratory volume in one second (FEV1) compared wi th placebo (mean differences (L) = placebo 0.05; formoterol 0.34; salm eterol 0.27; oxitropium bromide 0.23). Dose-dependent increases in FEV 1 were seen (mean values (L) before salbutamol and after a cumulative dose of 100, 200, 400, and 800 mu g - placebo: 1.06, 1.28, 1.35, 1.39, 1.41; formoterol: 1.33, 1.37, 1.41, 1.44, 1.44; salmeterol: 1.30, 1.3 3, 1.36, 1.39, 1.42; oxitropium bromide: 1.27, 1.34, 1.37, 1.41, 1.40) . Statistical analysis revealed no significant differences in FEV1 and forced vital capacity (FVC) responses to salbutamol after therapy wit h formoterol, salmeterol, or oxitropium bromide compared with placebo. This study clearly shows that a pretreatment with a conventional dose of formoterol, salmeterol, or oxitropium bromide does not preclude th e possibility of inducing a further bronchodilation with salbutamol in patients suffering from partially reversible chronic obstructive pulm onary disease.