Background and objective: Cyclooxygenase (COX) is an enzyme that converts arachidonic acid to prostanoids. There are two isoforms of COX, namely COX-1 and COX-2. COX-2 is highly inducible by several stimuli and is associated with inflammation. Recent studies have shown that COX-2 is upregulated in the airway epithelium of patients with asthma but little is known about the role it plays in cough,
a common symptom of bronchial asthma. This study was designed to investigate the role of COX-2 in cough reflex sensitivity in patients with asthma.

Patients and methods: The effect of etodolac, a potent COX-2 inhibitor, on cough response to inhaled capsaicin was examined in 17 patients with stable asthma in a randomized, placebo-controlled crossover study. Capsaicin cough threshold, defined as the lowest concentration of capsaicin eliciting 5 or more coughs, was measured as an index of airway cough reflex sensitivity.

Results: The geometric mean (geometric SEM) cough threshold was significantly increased after a 2-week treatment program with oral etodolac (200 mg twice a day) compared with placebo (36.7 [1.2] vs 21.6 [1.2] μM, P<.02).

Conclusions: These findings indicate that COX-2 may be a possible modulator augmenting airway cough reflex sensitivity in asthmatic
airways.

Key words: Airway cough reflex sensitivity. Capsaicin. Etodolac. COX-2. Bronchial asthma.