Capsaicin Cough Threshold in Chronic Cough Due to Postnasal Drip
This study is being done to find out why some people with mucus dripping down the back of their throat have a nagging cough while others do not cough.
|Study Design:||Observational Model: Case Control
Time Perspective: Prospective
|Official Title:||Capsaicin Cough Sensitivity, Airway Inflammation and Neurogenic Peptides in Chronic Cough Associated With Postnasal Drip|
- We hypothesize that capsaicin cough sensitivity is increased in patients with PND-CC compared to subjects with PND without cough and that cough sensitivity to capsaicin will decrease with treatment for postnasal drip. [ Time Frame: Endpoint ] [ Designated as safety issue: No ]
- We hypothesize that neurogenic inflammation is increased in patients with PND-CC compared to subjects with PND alone. [ Time Frame: Endpoint ] [ Designated as safety issue: No ]
- We hypothesize that nasal mucosal inflammation is increased in patients with PND-CC compared to subjects with PND alone, and that nasal mucosal inflammation will be decreased following treatment for postnasal treatment. [ Time Frame: Endpoint ] [ Designated as safety issue: No ]
Biospecimen Retention: Samples Without DNA
Mucus will be quantified and protease inhibitors will be added after collection. The specimen will be coded to deidentify. It will be transported to laboratory for storage and analysis. The mucus collected from the posterior nasopharynx will be frozen and assayed simultaneously. Substance P and Neurokinin A will be measured by ELISA at the end of the study period.
|Study Start Date:||March 2006|
|Study Completion Date:||December 2008|
|Primary Completion Date:||December 2008 (Final data collection date for primary outcome measure)|
Post Nasal Drip and chronic cough
Post nasal drip and no cough
The objective of the protocol is to determine the pathogenesis of cough in diseases of the aerodigestive tract. There were over 24 million ambulatory chronic cough visits nationally in 1991 and over 8,000 visits in 2004 at MCR. Current guidelines for chronic cough are based on case series and on empirical expert opinions. Studies have implicated mucosal inflammation, heightened sensitivity of capsaicin cough receptors on peripheral nerves and elaboration of inflammatory mediators including tussigenic neuropeptides. There are gaps in our knowledge of what triggers cough in many disease states. For example, postnasal drip syndrome has been estimated to account for 70% of chronic cough, yet it is known that not all patients with postnasal drip have chronic cough. Our hypothesis is that there must be critical factor/s that cause cough in one patient with postnasal drip but not in another. This study will evaluate whether there exists differences in capsaicin cough sensitivity, neuropeptides levels and mucosal inflammation in patients with postnasal drip and chronic cough and compared to its natural control group, subjects with postnasal drip with and without chronic cough. After standard therapy to eliminate postnasal drip, repeat measurement of capsaicin sensitivity and nitric oxide levels will be obtained. There is a critical need to determine the mechanisms underlying cough for better management. The study results will provide insight and fill gaps in our knowledge and will serve to advance future work evaluating mechanisms of cough in other disease states including asthma, GERD, interstitial lung disease and smokers.