How Different Beta-2 Receptor Genotypes Affect an Asthmatic's Response to Regular Salmeterol Treatment

Not Applicable

Completed

Brief Summary: The purpose of the study is to find out how well a long-acting beta agonist like salmeterol works in people with different forms of the same gene. Our hypothesis is that asthmatics with the Arg/Arg genotype will have loss of bronchoprotection against exercise-induced asthma with regular salmeterol treatment, as compared to asthmatics with the Gly/Gly genotype.

Detailed Description: In many patients with asthma, exercise-induced bronchoconstriction is a common and oftentimes limiting characteristic. Inhaled β2-adrenoreceptor agonists like albuterol are the most effective treatments available for the relief of acute asthma symptoms. However, there is evidence that regular use may lead to adverse effects in some patients. Previous studies have shown that polymorphisms of the β2-adrenergic receptor can influence airway responses to regular inhaled beta-agonist treatment.

Pharmacogenetics is the study of how genetic differences influence the variability in patients' responses to therapy, both therapeutic and adverse. Genetic susceptibility and environmental factors both play major roles in the etiology of asthma. The strong familial clustering of asthma has lead to a surge of research into the genetic predisposition of asthma. The aim of the present study is to utilize a double-blinded prospective cohort study to investigate whether genotype-specific effects occur when assessing the duration of protection conferred against exercise-induced bronchoconstriction by regular salmeterol treatment.

Recruitment & Eligibility

Inclusion Criteria

Both male and female
18 to 50 years of age
Resting FEV1 ≥ 65% of predicted normal
Exercise-induced bronchoconstriction defined as a decrease in FEV1 of ≥ 20% following a standardized exercise challenge when compared to pre-exercise baseline FEV1 value measured 5 minutes before exercise
Must be Arg/Arg or Gly/Gly genotype

Exclusion Criteria

Long-acting beta agonist use within 12 weeks of the first exercise challenge
Smoking within past 12 months
Greater than 10-pack years smoking history
Unresolved signs and/or symptoms of an upper respiratory tract infection within 4 weeks of first exercise challenge
Asthma exacerbation within 4 weeks of first exercise challenge requiring change in type, dose or frequency of medications and/or an unscheduled visit to an health care provider, including emergency room or hospital
Subject has exercised or performed strenuous activity within 72 hours of the first exercise challenge
Subject has been exposed to cold air sufficient to provoke symptoms of bronchospasm within 2 hours of exercise challenge
In addition to asthma, the subject has an active, acute or chronic pulmonary disorder documented by history, physical examination, or chest x-ray
Subject has evidence of ischemic, valvular, hypertrophic, familial or other forms of heart disease that would put the subject at risk during exercise testing or that would interfere with the ability to achieve protocol-specified heart rates during exercise testing
Subject has used systemic corticosteroids within 1 month of first exercise challenge

Arm && Interventions

Group	Intervention	Description
Arg/Arg	salmeterol	Arg/Arg subjects on 2 week salmeterol treatment
Gly/Gly	salmeterol	Gly/Gly subjects on 2 week salmeterol treatment

Primary Outcome Measures

Name	Time	Method
Comparison of the Maximum Percent Fall in FEV1 After Exercise Challenge at the End of the 2-week Treatment Period Between Arg/Arg and Gly/Gly Patients	2 weeks after exercise challenge

Secondary Outcome Measures

Name	Time	Method
Comparison of the Maximum Percent Fall in FEV1 From Pre-salmeterol Baseline to the End of the 2-week Treatment Period Between Arg/Arg and Gly/Gly Patients	2 weeks from pre-salmeterol baseline
Comparison of the Maximum Percent Fall in FEV1 After 1st Dose of Salmeterol to the End of the 2-week Treatment Period Between Arg/Arg and Gly/Gly Subjects	2 weeks after 1st dose of Salmeterol