[Circadian rhythms in peak expiratory flow rate of asthmatic patients before and after treatment with beclomethasone dipropionate].

Asthmatic patients have a circadian rhythm in peak expiratory flow rate (PEFR). The present study was done to measure the effect of inhaled beclomethasone dipropionate (BDP) on the circadian rhythm of PEFR in asthmatic patients. After two weeks of observation, BDP (400 micrograms) was given by metered dose inhaler to nine asthmatic patients. The dose of inhaled BDP (800-1200 micrograms) was increased every two weeks until PEFR varied by no more than 20% each day. PEFR was measured four times daily: on waking, around noon, in the evening, and at bedtime. Nine asthmatic patients had a significant (p < 0.05) rhythm detectable by single cosinor analysis, both during the observation period and during treatment. Analysis by the group mean-cosinor method showed that the mean mesor was 397.3 +/- 6.8 l/min, the mean amplitude was 54.3 +/- 7.1 l/min, and the mean acrophase was at 16:31 +/- 0.27 before treatment. After treatment, the mean mesor was 543.8 +/- 4.4 l/min, the mean amplitude was 30.5 +/- 4.9 l/minm, and the mean acrophase was at 16:25 +/- 0.31. The mean mesor had increased significantly (p < 0.05), and the mean amplitude had decreased significantly (p < 0.05) after treatment. The mean acrophase did not change. These data indicate that inhaled BDP increases PEFR at a constant acrophase in asthmatic patients.