Tachyphylaxis following regular use of formoterol in exercise-induced bronchospasm.
BACKGROUND
Formoterol is a highly effective therapeutic agent in the prevention of exercise-induced bronchospasm (EIB). Regular use of beta-adrenergic drugs may result in a reduction in the protective effect afforded by these bronchodilators against bronchoconstrictor stimuli. It is unknown whether this effect extends to formoterol and exercise.


METHODS
We performed a randomized, double-blind, parallel clinical trial in 19 patients with EIB. Each patient received inhaled formoterol or placebo twice daily during 4 weeks. Patients performed two exercise tests in a cycle ergometer on the 1st, 14th, and 28th study days separated 3 hours from each other. A dose of formoterol was given 30 min prior to the 2nd test.


RESULTS
There were significant differences in bronchoprotection between days 1 and 14 (p = .012) and between days 1 and 28 (p = .012) in the formoterol group. No differences were found in the placebo group. The evolution of the bronchoprotection index was also significantly different between the formoterol and the placebo group (p = .002) from day 1 to 28.


CONCLUSIONS
Tachyphylaxis developed to the protective effect of formoterol against EIB after 4 weeks of regular dosing. Tolerance was already found on day 14, though not progressive. Formoterol should be recommended only as needed in EIB.
García
R
R
Complejo Hospitalario de Ciudad Real, Allergy Unit, Spain. rgarcia@hnsa.insalud.es
Guerra
P
P
Feo
F
F
Galindo
P A
PA
Gómez
E
E
Borja
J
J
Fernandez-Pacheco
R
R
D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use; D000328:Adult; D001250:Asthma, Exercise-Induced / Q000188:drug therapy* / Q000503:physiopathology; D001993:Bronchodilator Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D004311:Double-Blind Method; D004983:Ethanolamines / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D000068759:Formoterol Fumarate; D006801:Humans; D008297:Male; D013618:Tachyphylaxis; D013997:Time Factors
D000318:Adrenergic beta-Agonists; D001993:Bronchodilator Agents; D004983:Ethanolamines; D000068759:Formoterol Fumarate