Abstract
Ten patients with bronchial asthma were challenged with histamine before and after receiving saline and active drug (levomepromazine or antazoline) (a total of six challenges). The antihistaminic effect of levomepromazine (25 mg) was found to be comparable to that of antazoline (100 mg), evaluated from skin prick tests. Prechallenge forced expiratory volume in one second (FEV1) was found to be larger after levomepromazine than after antazoline (p less than 0.05), indicating a direct bronchodilating effect. This increased threshold airway calibre may have influenced the results of challenge, but change in provocative concentration producing 20% fall (PC20) was not statistically significantly correlated to change in FEV1. Levomepromazine increased PC20 2-doubling concentration compared to antazoline (p less than 0.05). Variation was observed in two minutes' ventilation during tidal volume breathing challenge. However, there was no statistically significant variation in two minutes' ventilation during challenge after receiving levomepromazine or antazoline. It was concluded that levomepromazine possesses a bronchodilating capacity and reduces bronchial hyperreactivity.
