A comparison between inhaled clenbuterol and salbutamol in chronic bronchitis with reversible airway obstruction.

Twenty-one patients with chronic bronchitis and reversible airway obstruction participated in two single-blind, cross-over, placebo-controlled studies in inhaled clenbuterol - a new bronchodilator - and salbutamol. Nine patients participated in a dose-response study. Clenbuterol 10 microgram/puff, salbutamol 100 microgram/puff and placebo, were given by pressurized aerosol in cumulative doses of 1, 2, 4, 8, and 16 inhalations of each drug and placebo. The mean peak % FEV1 increases above the baseline were similar after all doses of clenbuterol and salbutamol and were significantly greater than after placebo. No cardiovascular effects were observed. Tremors were noted in two patients after 160 microgram clenbuterol and in one patient after 1600 microgram salbutamol. In a second study, clenbuterol (20 microgram), salbutamol (200 microgram) - two equieffective doses - and placebo were compared in a 6 h period in 12 patients. Clenbuterol and salbutamol produced bronchodilation of comparable magnitude, onset of action (15 min) and duration (4-6 h). Clenbuterol is an effective bronchodilator and, on the basis of molecular weight, about ten times more potent than salbutamol when given by aerosol.