title: Refractoriness to inhaled mannitol 3 hours after allergen challenge.
abstract: BACKGROUND
  A positive response to indirect airway challenges (eg, mannitol) that cause release of mast cell mediators causes refractoriness to a repeat exposure to the same or different indirect stimulus that lasts for at least several hours. Allergen challenge causes increased response to methacholine measured at 3 hours.
  
  
  OBJECTIVE
  To compare allergen-induced changes in airway response to methacholine and mannitol 3 hours after completion of an allergen challenge.
  
  
  METHODS
  Ten atopic patients with asthma completed a randomized clinical trial. The provocation concentration of methacholine causing a 20% decrease in forced expiratory volume in 1 second (FEV1) was measured 24 hours before and 3 hours after a standard allergen challenge. The provocation dose of mannitol causing a 15% decrease in FEV1 was also measured 24 hours before and 3 hours after allergen challenge. The allergen challenges were separated by 7 to 14 days.
  
  
  RESULTS
  The allergen-induced early responses, expressed as the maximum (SD) percent decrease in FEV1, were 29.7% (11.1%) and 27.8% (7.6%) on the methacholine and mannitol days, respectively. Airway response to methacholine increased significantly after allergen challenge (P = .02). By contrast, the airway response to mannitol was reduced by almost a doubling dose (P = .02) after allergen.
  
  
  CONCLUSIONS
  Three hours after allergen challenge at a time when the airways are more responsive to methacholine, there is a significant refractoriness to the indirect stimulus mannitol.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT01699594.
authors.affiliation: Division of Respirology, Critical Care and Sleep Medicine, Department of Medicine, University of Saskatchewan, Royal University Hospital, Saskatoon, Saskatchewan, Canada.
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Amakye
authors.forename: Beth E
authors.initials: BE
authors.lastname: Davis
authors.forename: Alexandra L
authors.initials: AL
authors.lastname: Martin
authors.forename: Gregory E
authors.initials: GE
authors.lastname: Peters
authors.forename: Donald W
authors.initials: DW
authors.lastname: Cockcroft
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000485:Allergens / Q000008:administration & dosage*; D001249:Asthma / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000209:etiology / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006967:Hypersensitivity / Q000503:physiopathology; D008297:Male; D008353:Mannitol / Q000008:administration & dosage*; D016210:Methacholine Chloride / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D000485:Allergens; D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D008353:Mannitol