Doseeffect Relationship of the flAgonists Fenoterol and Salbutamol in Patients With Asthma*

Q uestion: What is the relative per microgram potency and side effect profile of the 8-agonists salbutamol and fenoterol? Method: The relative bronchodilator ( FEV1, V25, V50) potency and side effect profile ( tremor, heart rate, breathlessness, BP) of nebulized salbutamol and fenoterol were evaluated by means of a randomized, doubleblind, crossover, cumulative (50 to 2,500 g) doseresponse study. Both fl-agonists were administered to 12 patients with stable asthma over age 18 years with baseline FEY1 between 35 to 70 percent predicted. Results: (1) Salbutamol and fenoterol both provided significant bronchodilatation compared with baseline. (2) There was no dose-effect difference between the two -agonists with respect to bronchodilator response. (3) Overall there was no significant difference between the side effect profiles of the two -agonists, although at the highest dose of fenoterol, there was marginally greater tremor when measured by accelerometry. (4) There was no difference in the vital signs or subjective patient evaluations of tremor, palpitations, or breathlessness as