Adrenaline and nocturnal asthma.

OBJECTIVE--To determine whether the nocturnal fall in plasma adrenaline is a cause of nocturnal asthma. DESIGN--Double blind placebo controlled cross-over study. In the first experiment the nocturnal fall in plasma adrenaline at 4 am was corrected in 10 asthmatic subjects with an infusion of adrenaline after parasympathetic blockade with 30 micrograms/kg intravenous atropine. In the second experiment 11 asthmatic subjects showing similar variations in peak expiratory flow rate had the nocturnal fall in plasma adrenaline corrected by infusion before atropine was given. PATIENTS--Asthmatic subjects with a diurnal variation in home peak expiratory flow rate of greater than 20% for at least 75% of the time in the two weeks before the study. MAIN OUTCOME MEASURES--Peak expiratory flow rate and plasma adrenaline. RESULTS--Correction of the nocturnal fall in plasma adrenaline at 4 am to resting 4 pm levels did not alter peak expiratory flow rate either before or after parasympathetic blockade with atropine. CONCLUSION--A nighttime fall in plasma adrenaline is not a cause of nocturnal asthma.