title: 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 (< or = 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 FEV1 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.
authors.affiliation: Department of Clinical Pharmacology, Royal Postgraduate Medical School, London.
authors.forename: J C
authors.initials: JC
authors.lastname: Henderson
authors.forename: F
authors.initials: F
authors.lastname: O'Connell
authors.forename: R W
authors.initials: RW
authors.lastname: Fuller
mesh_terms: D000328:Adult; D001249:Asthma / Q000175:diagnosis / Q000503:physiopathology*; D001985:Bronchial Provocation Tests / Q000379:methods; D016084:Bronchoconstriction / Q000187:drug effects*; D002110:Caffeine / Q000494:pharmacology*; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology; D006633:Histamine Antagonists / Q000494:pharmacology*; D006801:Humans; D008297:Male; D013997:Time Factors
chemical_list: D006633:Histamine Antagonists; D002110:Caffeine; D006632:Histamine