TUSSIVE EFFECT OF CAPSAICIN IN PATIENTS WITH GASTROESOPHAGEAL REFLUX WITHOUT COUGH

The aim of this study was to clarify the influence of gastroesophageal reflux (GER) on cough threshold in patients with digestive symptoms b ut free from respiratory involvement. Of 57 consecutive subjects refer red for 24-h esophageal pH monitoring because of digestive reflux symp toms, 29 patients free from respiratory disorders were studied. They u nderwent esophageal pH monitoring and manometry, upper gastrointestina l endoscopy, pulmonary function tests, and methacholine and capsaicin challenges The methacholine test was performed by inhalation of increa sing doses of methacholine up to 4,000 mu g; the results were expresse d as the dose causing a 20% decrease in FEV(1) from baseline (PD20). T he capsaicin threshold was evaluated by inhalation of increasing doses of capsaicin from 0.3 up to 9.84 nmol, expressing the results as the dose of capsaicin eliciting five coughs (PD,). Fifteen patients were c onsidered refluxers on the basis of a total esophageal acid exposure t ime above 4.7%. Esophagitis grade 0 was found in 15 patients, grade 1 in seven patients, grade 2 in seven patients. PD5 was significantly lo wer in refluxers (median 0.51 mu g, range 0.22 to 19.8) than in nonref luxers (19.8 mu g, range 0.31 to 19.8) (p < 0.001); there was no diffe rence in baseline ventilatory parameters and in airway responsiveness to methacholine between the two groups. All patients with a pathologic acid exposure time but one had a low cough threshold, irrespective of the presence or absence of esophagitis. We conclude that 1) patients with gastroesophageal reflux but without respiratory symptoms have a r educed cough threshold; 2) the enhanced cough response to capsaicin se ems to be due to acid reflux rather than to esophagitis; 3) the acid r eflux seems to be only a cofactor of cough and not a fully causative a gent.