In stable AIA, though not in ATA, there is a steady release of PGD(2) into the blood, accompanied by the release of tryptase. Aspirin enhances this reaction in most patients. Release of bronchoconstrictive PGD(2) might contribute to the severe clinical course of AIA.

In a subset of patients with asthma, aspirin and several other non-steroidal anti-inflammatory drugs (NSAID) that inhibit simultaneously cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) precipitate dangerous asthmatic attacks. We tested the hypothesis that in patients with aspirin-induced asthma the attacks are triggered by inhibition of COX-1 and not COX-2. In twelve asthmatic patients (seven men, five women, average age 39 years) oral aspirin challenge precipitated symptoms of bronchial obstruction with fall in FEV1 > 20%, and a rise in urinary leukotriene E4 (LTE4) excretion; also in five patients the stable metabolite of PGD2, 9alpha11betaPGF2, increased in urine. The patients then entered a double-blind, placebo-controlled, cross-over study in which they received either placebo or rofecoxib in increasing doses 1.5-25.0 mg for 5 consecutive days, separated by a 1-week wash-out period. No patient on rofecoxib developed dyspnoea or fall in FEV1 > 20%; mean urinary LTE4 and 9alpha11betaPGF2 urinary levels, measured on each study day for 6 h post-dosing, remained unchanged. Two patients on placebo experienced moderate dyspnoea without alterations in urinary metabolites excretion. At least 2 weeks after completion of the study, all patients received on an open basis 25 mg rofecoxib without any adverse effects. NSAID that inhibit COX-1, but not COX-2, trigger asthmatic attacks in patients with asthma and aspirin intolerance. Rofecoxib can be administered to patients with aspirin-induced asthma.

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