Histamine-induced bronchial response after administration of placebo, salbutamol and a combination of a beta-2-adrenergic drug (fenoterol) with an anticholinergic agent (ipratropium bromide) in asymptomatic asthma patients.

We examined 12 non-smoking patients affected by extrinsic bronchial asthma in steady state. Histamine PD20 FEV1 was assessed 4 h after the administration of salbutamol 200 micrograms, a combination of fenoterol 200 micrograms and ipratropium bromide 80 micrograms, and placebo. Despite the absence of any relevant bronchodilator effect, both salbutamol and the combination fenoterol + ipratropium bromide showed a strong protective effect against the bronchial response to histamine compared to placebo, the combination being more effective than salbutamol (p less than 0.05). Our data suggest that, when bronchial challenges with histamine are performed, airway response may be a consequence of both a direct action of such an agent on H1 receptors and of an associated cholinergic reflex.