Lack of effect of i.v. prostacyclin on aspirin-induced asthma.

Inhibition of prostacyclin biosynthesis by aspirin might be expected to promote asthmatic attacks in aspirin-intolerant patients. In vitro, prostacyclin impedes generation of leukotrienes and opposes their bronchoconstrictive action. In a double-blind study we compared the effects of intravenous infusions of prostacyclin with those of its solvent on bronchoconstriction provoked by threshold doses of aspirin in nine known aspirin-sensitive asthmatics. The intensity of bronchial obstruction precipitated by aspirin was similar during prostacyclin and placebo infusions. There was no difference in other symptoms of intolerance, except for rhinorrhea which seemed accentuated by prostacyclin (possibly because of nasal vasodilatation). Our results suggest that either the inhibitory effects of prostacyclin on leukotrienes described in vitro do not apply in vivo, or the importance of leukotrienes has been overestimated in this type of asthma.