All of the following drugs can precipitate an acute attack of asthma EXCEPT:

COX inhibitors like aspirin, indomethacin, naproxen and phenylbutazone etc. inhibit the formation of PGs from arachidonic acid. This results in diversion of metabolism of arachidonic acid to produce LTs. A large excess of LTs is therefore produced with the use of NSAIDs. These drugs, therefore, can result in precipitation of acute attack of asthma (because LTs are bronchoconstriction). Glucocorticoids are useful in the treatment and prophylaxis of bronchial asthma.