DOSE-EFFECT RELATIONSHIP OF THE BETA-AGONISTS FENOTEROL AND SALBUTAMOL IN PATIENTS WITH ASTHMA

Question: What is the relative per microgram potency and side effect p rofile of the beta-agonists salbutamol and fenoterol? Method: The rela tive bronchodilator (Delta FEV(1), V25, V50) potency and side effect p rofile (Delta tremor, heart-rate, breathlessness, BP) of nebulized sal butamol and fenoterol were evaluated by means of a randomized, double- blind, crossover, cumulative (50 to 2,500 mu g) dose-response study. B oth beta-agonists were administered to 12 patients with stable asthma over age 18 years with baseline FEV(1) between 35 to 70 percent predic ted. Results: (1) Salbutamol and fenoterol both provided significant b ronchodilatation compared with baseline. (2) There was no dose-effect difference between the two beta-agonists with respect to bronchodilato r response. (3) Overall there was no significant difference between th e side effect profiles of the two beta-agonists, although at the highe st dose of fenoterol, there was marginally greater tremor when measure d by accelerometry. (4) There was no difference in the vital signs or subjective patient evaluations of tremor, palpitations, or breathlessn ess as estimated by a visual analogue scale. (5) No significant advers e reactions occurred. Summary and conclusion: Equivalent bronchodilata tion and similar side effect profiles were measured in a group of pati ents with stable asthma after treatment with nebulized salbutamol or f enoterol in the dose range 50 to 1,250 mu g (cumulative, 2,500 mu g). This indicates that both a-agonists have similar per microgram potency and side effect profiles. Observed clinical differences in response o r side effects associated with fenoterol metered-dose inhaler administ ration may be a result of its higher dose per puff metered-dose inhale r formulation.