title: Repeated histamine inhalation tests in asthmatic patients.
abstract: Histamine inhalation tests were performed in 12 asthmatic patients using a 2-min tidal breathing inhalation technique. The tests were repeated on separate days with 30-, 60-, and 120-min intervals between inhalation tests. On another day the inhalation tests were repeated four times with 40-min intervals between tests. The geometric mean provocative concentrations of histamine needed to cause a 20% fall in forced expiratory volume in 1 sec (PC20) for the group on the latter study day were 1.67, 1.57, and 1.55 mg/ml (p greater than 0.25) indicating no change in sensitivity to inhaled histamine with repeated testing. The results suggest that cumulative dose-response curves for drugs potentially affecting the airways or antagonizing histamine can be constructed within 1 day using histamine inhalation tests. The data also suggested that an individual PC20 result may be sensitively assessed by comparing it to a +/- 2 SD range from the mean of a series of control or placebo PC20 values.
mesh_terms: D000328:Adult; D001249:Asthma / Q000175:diagnosis*; D001985:Bronchial Provocation Tests; D005260:Female; D005541:Forced Expiratory Volume; D006632:Histamine / Q000008:administration & dosage*; D006801:Humans; D007108:Immune Tolerance; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D006632:Histamine