The effect of 443C81, a mu opioid receptor agonist, on the response to inhaled capsaicin in healthy volunteers.

Abstract

Activation of mu opioid receptors on sensory nerves in the lung represents an attractive mechanism for reducing cough and reflex bronchoconstriction. We have examined the effect of the peptide 443C81, a peripherally acting mu opioid agonist, on the cough and reflex increase in respiratory resistance (Rrs) produced by capsaicin in nine healthy male volunteers. Using a randomised, double‐blind crossover design, each subject inhaled either saline, 1 mg ml‐1 443C81 or 4 mg ml‐ 1 443C81 for 10 min from an ultrasonic nebuliser. The cough response to a range of doses of inhaled capsaicin and the increase in Rrs caused by inhalation of a single subtussive dose of capsaicin were measured before and after each treatment. There was no evidence of an effect of either 1 or 4 mg ml‐1 443C81 on cough or increase in Rrs produced by capsaicin when compared with the saline placebo. It is concluded that inhalation of this mu opioid receptor agonist had no effect on capsaicin‐induced cough or reflex bronchoconstriction in healthy volunteers. 1991 The British Pharmacological Society