INHALED NICOTINE IN HUMANS - EFFECT ON THE RESPIRATORY AND CARDIOVASCULAR SYSTEMS

Inhalation of nicotine (0-64 mg/ml) and capsaicin (2 X 10(-6)-2.5 X 10 (-4) M) in 24 healthy nonsmoking subjects produced a concentration-dep endent cough response. Two subjects coughed to capsaicin but not to ni cotine. The mean (95% confidence interval) nicotine concentrations cau sing two and five coughs were 5.5 (3.5-8.7) and 15.8 (10.0-25.1) mg/ml , respectively, and were reproducible over 3 different days. Capsaicin inhalation did not alter the response to nicotine and vice versa. Bot h agents increased respiratory resistance, but the response was more r apid to capsaicin. Inhalation of nicotine (0-8 mg/ml) over 5 min cause d increases in heart rate and blood pressure and a decrease in skin te mperature. Inhaled ipratropium bromide (0.50 mg) had an antitussive ef fect and also inhibited the nicotine-induced bronchoconstriction, indi cating a vagally mediated effect. Sodium cromoglycate (0.20 mg) did no t affect cough or airway resistance changes caused by nicotine. This s tudy shows that inhaled nicotine produces a concentration-dependent co ugh and airway obstruction in healthy subjects, probably because of st imulation of afferent nerve endings in the bronchial mucosa and mediat ed through parasympathetic cholinergic pathways. Respiratory reflexes evoked by nicotine are similar to those produced by capsaicin, but it is unclear whether these reflexes are mediated by the same type of sen sory nerves.