Beta2-adrenoceptor regulation and bronchodilator sensitivity after regular treatment with formoterol in subjects with stable asthma.
OBJECTIVE
We have previously found that beta2-adrenoceptor downregulation and bronchodilator desensitization to albuterol occurred at 36 hours after stopping regular treatment with twice daily salmeterol. In this study we have evaluated these same effects with formoterol given once or twice daily on a regular basis.


METHODS
In a randomized, placebo-controlled, double-blind, double-dummy crossover study, 16 subjects with mild-to-moderate stable asthma (mean [SD] age, 32.5 [15.3] years; mean [SD] FEV1, 73.2 [12.1] percent predicted) receiving regular inhaled corticosteroid therapy received 1 week of treatment with formoterol dry powder (24 microg twice daily [8 AM/8 PM]), formoterol (24 microg once daily [8 PM]), or identical placebo. Lymphocyte beta2-adrenoceptor parameters and a dose-response curve to inhaled albuterol (200 to 1600 microg) were evaluated at 36 hours after the last dose of each treatment period.


RESULTS
There were no significant differences in the mean values for albuterol dose-response effects among the three treatment regimens. Comparison of maximal bronchodilator responses between treatments (mean and SEM as change from baseline) revealed no significant differences between treatments for FEV1 (0.47 L [0.06 L] for placebo vs 0.48 L [0.07 L] for 24 microg once daily formoterol vs 0.51 L [0.08 L] for 24 microg twice daily formoterol) or for forced expiratory flow, mid-expiratory phase (FEF25-75) (0.80 L/sec [0.12 L/sec] for placebo vs 0.80 L/sec [0.16 L/sec] for 24 microg once daily formoterol vs 0.89 L/sec [0.14 L/sec] for 24 microg twice daily formoterol). Formoterol also had no significant effect on mean lymphocyte beta2-adrenoceptor density. However, in five of seven patients with the homozygous Gly-16 polymorphism, beta2-adrenoceptor density was downregulated by twice daily formoterol, whereas only two such cases exhibited a reduction in maximal FEV1 response to albuterol.


CONCLUSIONS
The results of this study showed that for patients taking inhaled corticosteroids, overall beta2-adrenoceptor regulation and associated bronchodilator sensitivity to inhaled albuterol were unaltered at 36 hours after stopping regular treatment with formoterol. However, in a subset of patients who were Gly-16 homozygous, there was a tendency towards downregulation but not desensitization. Further studies in subjects with more severe asthma are required to assess the clinical relevance of these findings.
Aziz
I
I
Department of Clinical Pharmacology and Therapeutics and Respiratory Medicine, Ninewells Hospital and Medical School, University of Dundee, Scotland, United Kingdom.
Hall
I P
IP
McFarlane
L C
LC
Lipworth
B J
BJ
D000280:Administration, Inhalation; D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage / Q000627:therapeutic use; D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000627:therapeutic use*; D000328:Adult; D000420:Albuterol / Q000008:administration & dosage / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy*; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004983:Ethanolamines / Q000008:administration & dosage / Q000627:therapeutic use*; D005260:Female; D005541:Forced Expiratory Volume; D000068759:Formoterol Fumarate; D005998:Glycine / Q000235:genetics; D006339:Heart Rate; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008450:Maximal Midexpiratory Flow Rate; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000235:genetics / Q000378:metabolism
D000305:Adrenal Cortex Hormones; D000318:Adrenergic beta-Agonists; D001993:Bronchodilator Agents; D004983:Ethanolamines; D011943:Receptors, Adrenergic, beta; D000420:Albuterol; D005998:Glycine; D000068759:Formoterol Fumarate