[Effect duration and treatment effectiveness of salmeterol, fenoterol and salbutamol in severe forms of respiratory tract obstruction].

Duration and intensity of bronchodilator action of 0.2 mg Fenoterol, 0.2 mg Salbutamol, and 0.05 mg Salmeterol were investigated in 15 subjects with COPD over a period of 12 hours. Airway resistance and FEV1 were measured and subjective side effects noted. Salbutamol MDI was used as rescue medication. Airway resistance and FEV1 demonstrated significant bronchodilation with all bronchodilator drugs after 15 min and maximum bronchodilation between 1 and 2 hrs. After 3 to 5 hrs. bronchodilator effects of fenoterol and salbutamol are lost by at least 50%, whereas this effect is only seen after 8 to 9.5 hrs. with salmeterol. There were considerable individual differences of the efficacy of all three drugs. However, salmeterol was equally efficaceous, compared to fenoterol and salbutamol, but its duration was at least twice as long. Consequently, rescue medication was used in only about 50% of the cases. Side effects of all substances were comparable. From these data it may be concluded that the efficacy of beta2-adrenergic agonists is comparable, irrespective of the duration of action of a single administration, if repeated administrations are used with short acting substances. In addition, this study confirmed that in individual patients a) the response to beta2-adrenergic agonists is variable and b) that different lung function parameters such as airway resistance and FEV1 may give different results.