Nedocromil sodium inhibits the response to exercise-induced asthma (EIA). M
annitol given as a powder by inhalation is an osmotic stimulus that identif
ies EIA. We studied the acute effect of nedocromil on airway responsiveness
to mannitol in 24 asthmatic subjects. After a control day, nedocromil (8 m
g) or its placebo was administered randomized, double blind, 10 min before
a challenge with progressively increasing doses of mannitol. Nedocromil inh
ibited the response to mannitol and there was a significant increase in the
dose of mannitol required to cause a 15% reduction in FEV1 (PD15) after ne
docromil 409 (316,503) mg compared with placebo 156 (106,229) mg (p < 0.001
). In the presence of nedocromil 12 subjects no longer recorded a 15% decre
ase in FEV1 in response to mannitol. The remaining 12 required a significan
tly greater dose of mannitol to achieve a 15% decrease in FEV1 after nedocr
omil. Following nedocromil, a plateau in responsiveness to mannitol was obs
erved in 14 subjects. Nedocromil significantly inhibits the responsiveness
to inhaled mannitol in asthmatic subjects.