Effect of naloxone on circadian rhythms in lung function.

To determine whether the endogenous opioid peptides play a part in the pathogenesis of asthmatic morning dipping, six patients with chronic asthma with a reproducible peak flow pattern of morning dipping were investigated in a double blind, randomised, crossover study of naloxone versus placebo. Naloxone was given as a loading dose of 8 mg followed by a continuous infusion of 5.6 mg/h from midnight until 10 am on two consecutive nights. Naloxone had no significant effect on PEFR, FEV1, or FVC at 6 am. There was, however, an improvement over placebo values in all these indices between the hours of 8 am and 8 pm on the day after the first naloxone infusion in all six patients. This effect was not observed after the second naloxone infusion.