DECREASE OF HISTAMINE-INDUCED BRONCHOCONSTRICTION BY CAFFEINE IN MILDASTHMA

Background-While high doses of caffeine may affect pulmonary function and bronchial challenge tests in patients with mild asthma, the effect s of lower doses (less-than-or-equal-to 5 mg/kg) are less well documen ted. Specific recommendations exist for withholding theophylline, but not caffeine, before bronchoprovocation and pulmonary function testing . Methods-To assess the effect of a single oral dose of caffeine (5 mg /kg) on FEV1 and bronchial responsiveness to histamine a double blind, placebo controlled study was performed in eight patients with mild st able asthma. Results-While caffeine had no effect on FEV1, mean (95% c onfidence interval) log PC20 histamine was significantly higher 150 mi nutes [caffeine = 0.99 (0.2) mg/ml, placebo = 0.53 (0.29)] and 240 min utes [caffeine = 0.89 (0.24), placebo = 0.44 (0.26)] after administrat ion of caffeine than after placebo. Conclusions-Caffeine should be exc luded from the diet for a period of more than four hours before bronch ial provocation testing. The exact length of time for which it must be excluded requires further study.