Reduced protection against exercise induced bronchoconstriction after chronic dosing with salmeterol

Area of Science:

• Pulmonology
• Pharmacology

Background:

• Exercise-induced bronchoconstriction (EIB) is a common condition in asthma patients.
• Long-acting beta-agonists like salmeterol are used to manage asthma symptoms.

Purpose of the Study:

• To evaluate the protective effect of inhaled salmeterol against EIB after single versus chronic dosing.
• To compare the duration of action of salmeterol after initial use and after 4 weeks of twice-daily administration.

Main Methods:

• A randomized, double-blind, crossover study involving 12 patients with exercise-induced asthma.
• Standardized exercise tests were conducted 6 and 12 hours post-dose on the first and last days of treatment.
• Salmeterol (50 mcg) twice daily for 4 weeks was compared against a placebo.

Main Results:

• Salmeterol provided significant protection against EIB at 6 and 12 hours after the first dose compared to placebo.
• No significant attenuation of EIB was observed after 4 weeks of chronic salmeterol treatment.
• The percentage fall in FEV1 post-exercise was significantly lower with salmeterol after the first dose (11.9%) versus placebo (34.8%), but not after 4 weeks (24.0% vs. 32.9%).

Conclusions:

• Initial single dosing of inhaled salmeterol effectively protects against EIB.
• Chronic, twice-daily dosing of salmeterol for 4 weeks may lead to diminished protection against EIB.
• Tachyphylaxis, a rapid decrease in drug response, might develop with prolonged salmeterol use for EIB.