The effects of capsaicin inhalation on exhaled nitric oxide (NO) in healthy human subjects

P. Suwanprathes, M. G. Ngu, A. B X Breslin, D. H. Yates, P. M. Maclean, A. J. Ing

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The source of exhaled NO in human subjects has been found to arise from a number of different sites, including pulmonary vascular endothelium, bronchial epithelial cells and macrophages. Non adrenergic, non-cholinergic nerves (NANC) may also produce NO, and the aim of this study was to investigate the effect of a potent airway nerve stimulator (capsaicin), on exhaled NO in healthy subjects and patients with cough. We report our initial findings in healthy subjects. Methods: 14 healthy subjects with no cough or evidence of bronchial asthma underwent single breath capsaicin. All subjects inhaled serial doses of capsaicin from 5.1p.mol to 330(jimol. Exhaled NO was measured prior to capsaicin inhalation, and both 5 and 30 min after inhalation. Results: Data analysed with paired Wilcoxon rank sum test. Pre capsaicin NO* Post (5 min) NO# Post (30min) NO + p value ppb log No ppb log No ppb log No *vs# *vs + #vs + Median 22 1.34 16.5 1.22 21.5 1.33 0.001 0.074 0.004 Range 15- 1.18- 8-87 0.90- 10- 1.00-142 2.15 1.94 138 2.14 Conclusions: Exhaled NO levels fell significantly 5 min after inhalation of capsaicin, and returned to baseline levels after 30 min. This finding is against our initial hypothesis that capsaicin may stimulate NANC and thus increase exhaled NO. The explanation for our findings are uncertain, but suggest that capsaicin transiently suppresses airway NO production, possibly via negative feedback neuronal reflexes.

Original languageEnglish
Issue numberSUPPL. 1
Publication statusPublished - 1999
Externally publishedYes


  • Capsaicin, cough
  • Exhaled nitric oxide
  • NANC


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