Sodium cromoglycate and atropine block the fall in FEV1 but not the cough induced by hypotonic mist.

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Abstract
In a group of patients with mild asthma the inhalation of mist derived from ultrasonically nebulized distilled water caused an increase in cough and a fall in FEV1 [forced expiratory volume in 1 s]. Double blind administration for 5 min of sodium cromoglycate (from an original solution containing 30 mg/ml) or atropine (2 mg/ml) by inhalation from a Minineb nebulizer, 30 min before the mist challenge, caused a significant reduction in the fall in FEV1 (P < 0.05), but not in cough, by comparison with the protection afforded by placebo (saline). In a 2nd study the fall in FEV1 caused by the inhalation of distilled water was not significantly different from that seen in response to hypotonic NaCl (1.7 g/l, 58 mmol/l), but both produced a significantly greater fall than did a similar mist containing sodium cromoglycate at an original concentration of 10 mg/ml (58 mmol/l). Both atropine and sodium cromoglycate can block the fall in FEV1 due to mist and protection by sodium cromoglycate is immediate. Sodium cromoglycate apparently blocks the nervous reflexes concerned in the response to mist, probably in the afferent limb of the reflex.