Dose-response characteristics of nebulized isoproterenol in asthmatic children

Abstract

The optimal dose of nebulized isoproterenol for nontoxic bronchodilation in asthmatic children is not established. In this study the response of 23 asthmatic children to four doses of nebulized isoproterenol hydrochloride, 1:200, a metered dose form of isoproterenol, and placebo were compared for onset, duration, and degree of bronchodilatation as well as cardiovascular responses and side effects. Data, including forced expiratory volume in 1 sec (FEV 1), maximum mid-expiratory flow (MMEF), heart rate, and blood pressure obtained before and at 5, 15, 30 and 60 min after each test nebulization, were analyzed. The results show that all doses of isoproterenol produced significant bronchodilatation at all times. The lowest dose of nebulized isoproterenol produced bronchodilatation which was initially equal to the higher doses but was significantly less effective at 60 min. There was no significant difference in the bronchodilator response to doses 2, 3, and 4. There was, however, a progressive increase in heart rate with increasing doses of isoproterenol, but significant effects were observed on blood pressure only with doses 3 and 4. We conclude that a dose of 0.005 ml/kg (0.025 mg/kg) of inhaled isoproterenol by the nebulization technique described and using the same equipment (air compressor, T tube apparatus, and nebulizer) is optimal for bronchodilatation in asthmatic children with minimal cardiovascular side effects.