title: Theophylline minimally inhibits bronchoconstriction induced by dry cold air inhalation in asthmatic subjects.
abstract: The aim of this study was to evaluate the effect of a sustained-release theophylline preparation on bronchial responsiveness to cold dry air inhalation in asthmatic subjects. Sixteen adult subjects with asthma in a clinical steady state underwent 3 isocapnic cold air challenges on 3 consecutive days at a time when they had not received oral theophylline medication over the past 3 days. The dose of cold air causing a 20% (PD20) fall in FEV1 was obtained from each subject's dose-response curve. Subjects were then administered active or placebo sustained-release theophylline preparations according to a double-blind, randomized, two-treatment crossover design. Medication was given for a minimum of 3 consecutive days. PD20 was reassessed on 4 different days, 3 to 4 h after receiving active or placebo medication (two visits for each medication). We found a significant bronchodilator effect of theophylline as compared to the placebo (mean +/- SD differences in changes of FEV1 of 8.8 +/- 1.9%). We also documented a significant blocking effect of the active medication as opposed to the placebo on PD20 (p = 0.01). This difference (mean = 0.18 on the loge scale) was statistically beyond the intraindividual between-day variability observed on the 3 control days (p less than 0.001) but was physiologically minimal. This blocking effect was also partially related to changes in airway caliber. We conclude that theophylline showed a blocking effect on bronchial responsiveness to dry cold air, which was physiologically minimal and was partially related to changes in airway caliber.
authors.affiliation: Department of Chest Medicine, Hôpital du Sacré-Coeur, Montreal, Quebec, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Merland
authors.forename: A
authors.initials: A
authors.lastname: Cartier
authors.forename: J
authors.initials: J
authors.lastname: L'Archevêque
authors.forename: H
authors.initials: H
authors.lastname: Ghezzo
authors.forename: J L
authors.initials: JL
authors.lastname: Malo
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D001986:Bronchial Spasm / Q000209:etiology / Q000517:prevention & control*; D003080:Cold Temperature; D003692:Delayed-Action Preparations; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006813:Humidity; D008297:Male; D008450:Maximal Midexpiratory Flow Rate; D008875:Middle Aged; D011897:Random Allocation; D012119:Respiration; D013806:Theophylline / Q000097:blood / Q000627:therapeutic use*; D014797:Vital Capacity
chemical_list: D003692:Delayed-Action Preparations; D013806:Theophylline