Capsaicin-induced Cough in Humans

Abstract

We have evaluated the properties of capsaicin as a selective cough-inducing agent in healthy human subjects. Despite frequent coughing, the subjects could inhale repeated breaths of capsaicin aerosol during 60 s without difficulty. Cough started immediately on inhalation and was most intense during the first 30 s. Cough always disappeared promptly when the capsaicin inhalation was terminated. The cough response was well reproducible and concentration-dependent up to 10 microM; at higher concentrations there was a distinct plateau of the cough response. Specific airway conductance was not changed 3 min after 50 microM capsaicin. Capsaicin (> or = 10 microM) had a burning taste, but there were no visual signs of pharyngitis or laryngitis. Citric acid (nebulized solutions 0.125 to 32%) had a choking effect and could be administered only as single breaths. There was no correlation between the cough response to citric acid and to capsaicin. Inhaled lidocaine (20 and 80 mg from nebulized solutions) caused a dose-dependent inhibition of capsaicin-induced cough. Lidocaine suppressed citric acid-induced cough as effectively as capsaicin-induced cough. In conclusion, we have characterized capsaicin-induced cough and demonstrated that it can be a useful tool in the study of cough reactivity and for evaluation of antitussive agents in humans. Capsaicin may be complementary to citric acid and may offer experimental advantages over this traditional tussive stimulus.

Inhaled ethanol potentiates the cough response to capsaicin in patients with airway sensory hyperreactivity

“…The testing of cough sensitivity with capsaicin inhalation is otherwise often performed with a "single-breath" technique using increasing concentrations of capsaicin until the individual coughs, for example, two or five times (C2 or C5), which has shown a good reproducibility [41,42]. Others, who used both techniques, found that the tidal breathing method with a fixed time and concentration showed good reproducibility and dose-response relationship in the short term, as well as in the long term [8,43]. The single-breath technique was more dependent on a standardized inhalation technique compared to the fixed time and concentration technique [44].…”

“…After capsaicin inhalation, changed levels of nerve growth factor in nasal secretions have been detected, indicating a neurochemical imbalance in the airways, which is related to SHR [6]. Cough sensitivity to capsaicin is a measure of airway sensory reactivity [7,8]. Patients with SHR react more strongly than healthy individuals to provocation with inhaled capsaicin, and the cutoff values for a positive reaction have been determined [4].…”

Cough and ventilatory adjustments evoked by aerosolised capsaicin and distilled water (fog) in man

“…First, the phenomenon could be due to a steeper stimulus/response relationship for capsaicin than fog. Concentration-or dose-dependency of cough frequency has repeatedly been demonstrated for capsaicin (e.g., Midgren et al, 1992) but no data are available for fog. Since the present experiments were designed to investigate specifically the reflex respiratory responses evoked by threshold capsaicin and fog concentrations, they cannot provide information on the stimulus/response relationships for these tussigenic agents.…”

Atopy in cough sensitivity to capsaicin and bronchial responsiveness in young females

“…The reproducibility of sensitivity and of dose-response curve for capsaicininduced coughs has been established in normal subjects [17]. In this study, the cough threshold to inhaled capsaicin was measured as an index representing airway cough sensitivity, which was defined as the lowest concentration of capsaicin eliciting five or more coughs [2,4,6].…”