Attenuation of nocturnal asthma by cromakalim

In a randomised, double-blind, crossover study, single oral doses of cromakalim, a potassium-channel activator, or placebo were given to 23 patients with nocturnal asthma. There was a significant reduction (p less than 0.005) in the early morning fall in forced expiratory volume in 1 s (FEV1) after 0.5 mg cromakalim (fall 9.8% [SEM 3.2%]) compared with placebo (18.5 [2.8]%). In a repeat dosing study, administration of 0.25 mg and 0.5 mg cromakalim on 5 consecutive nights to a further group of 8 asthmatic subjects significantly reduced the early morning fall in FEV1 from 28.7 (6.5)% after placebo to 19 (4.2)% after 0.25 mg and 14.9 (6.5)% after 0.5 mg. Potassium-channel activators may be useful in the treatment of asthma, especially for nocturnal symptoms.