Dissociation in the effect of nedocromil on mannitol-induced cough or bronchoconstriction in asthmatic subjects.
Author(s): Koskela HO, Martens R, Brannan JD, Anderson SD, Leuppi J, Chan HK
Affiliation(s): Department of Respiratory Medicine, Kuopio University Hospital, Kuopio, Finland. firstname.lastname@example.org
Publication date & source: 2005-09, Respirology., 10(4):442-8.
Publication type: Randomized Controlled Trial
OBJECTIVE: Inhaled mannitol induces both bronchoconstriction and cough. Nedocromil sodium greatly attenuates mannitol-induced bronchoconstriction. Knowledge about the effect of nedocromil on mannitol-provoked cough might, therefore, clarify the mechanisms of this response. METHODOLOGY: Inhalation challenges with mannitol powder were performed after inhalation of 8 mg of nedocromil or its placebo in 24 subjects with asthma. The study was double-blind, randomised, and placebo-controlled. The mannitol-provoked coughs were manually recorded and the mannitol-induced bronchoconstriction was measured with a spirometer. RESULTS: The cumulative dose of mannitol that provoked at least two coughs tended to be higher on the nedocromil day than on the placebo day (34 (22--53) mg vs 26 (18--37) mg, P=0.051). The cumulative number of coughs per dose of mannitol was slightly, but significantly, lower on the nedocromil than on the placebo day (4.2 (2.8--6.3) coughs/100 mg vs 6.1 (4.0--9.4) coughs/100 mg, P=0.037). However, when analysed on a constant-dose basis, nedocromil provided no protection for coughing (-1% protection), whereas the protection for bronchoconstriction was clear (55% protection). CONCLUSIONS: Nedocromil strongly attenuates mannitol-induced bronchoconstriction but has a negligible effect on mannitol-provoked cough. Therefore, these responses seem to have different pathways in asthma. Recording of both provoked coughs and induced bronchoconstriction during mannitol challenge may provide supplementary information about a patient's disease.