Stimulation of exposed C-fibre afferent nerve endings by inflammatory mediators may contribute to airway
inflammation and bronchoconstriction in
asthma through the release of
neuropeptides from collateral nerve endings. The polar
opioid peptide 443c81 is a
mu-opioid receptor agonist which inhibits C-fibre activation and non-
cholinergic neurally mediated bronchoconstriction in animal models. We have compared the effect of
443c81 (5 ml of a 4 mg/ml
solution nebulized) four times daily for 7 days with placebo on
asthma control in a double-blind parallel group study of 40 subjects with mild
asthma. Twenty subjects (12 male, mean FEV1 83% predicted) received placebo and 20 (15 male, mean FEV1 91% predicted)
443c81 after a 1 week run-in. Efficacy was assessed by comparing changes from baseline values in FEV1, provocative dose of
histamine causing a 20% fall in FEV1 (PD20), symptom scores,
bronchodilator use and home peak flow readings.
443c81 had no acute effect on FEV1 and the mean changes in FEV1 after 1 week of treatment were not significantly different (placebo -0.9%;
443c81-3.8%). One hour after the first dose of
443c81 PD20 increased from a geometric mean of 0.88 to 1.48 mumol (mean change 0.76 doubling doses; 95% CI 0.23, 1.29) but this did not differ significantly from the change with placebo (mean difference between
443c81 and placebo 0.63 doubling doses; 95% CI -0.2, 1.5; P = 0.095). After 1 week's treatment, PD20 was similar to baseline values with
443c81 (0.78 mumol) and placebo (baseline 0.71, post-treatment 0.93 mumol).(ABSTRACT TRUNCATED AT 250 WORDS)