Comparison of Fenoterol and Orciprenaline with regard to Broncho-Dilating Action and β 2 – Selectivity

A double-blind crossover trial was performed comparing orciprenaline (10 mg) and fenoterol (5 mg) by oral administration in forty-four patients with bronchial asthma. Measurement of VC, FEV₁, respiratory impedance (ZR), blood pressure and pulse rate, and observation of subjective symptoms, rales and side-effects, were made over the 4 hours following oral administration of the drugs. FEV₁ increased through the 4 hours reaching a peak at 3 hours with both drugs. The per cent increase of FEV₁ was statistically significant at each measuring time for both drugs (p < 001), and was significantly larger in fenoterol than in orciprenaline at 2 and 3 hours (p < 0.05). ZR with fenoterol decreased from 2 hours to 4 hours with a significant difference from Z_R with orciprenaline (p < 0.05). Side-effects such as palpitation, finger tremor or headache were seen in 36.4% cases with fenoterol and 30.5% with orciprenaline, but the degree of the side-effects was minimal. Finger tremor was observed in one case with orciprenaline and ten cases with fenoterol. Palpitation was observed in five cases with each of the drugs. Because finger tremor seems to be due to β₂-stimulation and palpitation seems to be due to β₁-stimulation, fenoterol was supposed to be more β₂-selective than orciprenaline. In conclusion fenoterol had a high β₂ selectivity and a powerful and long-lasting broncho-dilating effect compared with orciprenaline.