Decrease of histamine induced bronchoconstriction by caffeine in mild asthma

Abstract

Background-While high doses of caffeine may affect pulmonary function and bronchial challenge tests in patients with mild asthma, the effects of lower doses (≤ 5 mg/kg) are less well documented. 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 FEV, and bronchial responsiveness to histamine a double blind, placebo controlled study was performed in eight patients with mild stable asthma. Results-While caffeine had no effect on FEV1, mean (95% confidence interval) log PC20 histamine was significantly higher 150 minutes [caffeine = 0 99 (0.2) mg/ml, placebo = 0 53 (0.29)] and 240 minutes [caffeine = 0-89 (0-24), placebo = 0 44 (0.26)] after administration of caffeine than after placebo. Conclusions-Caffeine should be excluded from the diet for a period of more than four hours before bronchial provocation testing. The exact length of time for which it must be excluded requires further study.