title: Modification of concentration-response curves to inhaled methacholine after the pollen season in subjects with pollen induced rhinitis.
abstract: BACKGROUND
  The effect of cessation of exposure to pollen on the concentration-response curves to inhaled methacholine was investigated.
  
  
  METHODS
  Methacholine inhalation challenges (up to 200 mg/ml) were performed in 13 non-asthmatic patients with grass and/or Parietaria pollen-induced rhinitis during the pollen season, and one and four months after it. Concentration-response curves were characterised by their PC20, position, and plateau.
  
  
  RESULTS
  Geometric mean methacholine PC20 increased from 6.4 mg/ml during the pollen season to 28.2 mg/ml and 54.9 mg/ml one and four months after the end of season, respectively. The mean (SE) level of the plateau decreased from 30.5 (4.3%) in the pollen season to 23.3 (3.7)% and 20.1 (3.3)% one and four months after the end of pollen season, respectively. Although the methacholine concentration that produced 50% of the maximal response increased from 2.9 mg/ml to 4.3 mg/ml and 6.0 mg/ml, the differences were not significant.
  
  
  CONCLUSIONS
  In non-asthmatic patients with pollen-induced rhinitis cessation of exposure to pollen is associated with significant modifications in the methacholine threshold value and level of plateau, and with a small shift in the concentration-response curves to the right.
authors.affiliation: Sección de Alergia, Hospital Dr Peset, Valencia, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Prieto
authors.forename: M
authors.initials: M
authors.lastname: López
authors.forename: J M
authors.initials: JM
authors.lastname: Bertó
authors.forename: A
authors.initials: A
authors.lastname: Peris
mesh_terms: D000328:Adult; D001985:Bronchial Provocation Tests; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D011058:Pollen; D012129:Respiratory Function Tests; D006255:Rhinitis, Allergic, Seasonal / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D016210:Methacholine Chloride