This is a randomized, cross-over, single-blind trial. Eligible patients will be randomly assigned to undergo either capsaicin or adenosine triphosphate (ATP) cough provocation test, followed by a washout period of 2 to 14 days. Participants will be crossed-over to undergo another cough provocation test. Patient would be under observation in the out-patient clinics for \~2 hours following the cough provocation tests in case of severe adverse events.
This is a randomized, cross-over, single-blind trial. After verification of the entry criteria, eligible patients will be, based on the randomization codes, randomly assigned to undergo either capsaicin or ATP cough provocation test (the participants will inhale capasaicin or ATP incremental concentration to induce cough, meanwhile the number of coughs and adverse events will be recorded in each concentration during the first 30 seconds), followed by a washout period of 2 to 14 days (no major changes in the use of concomitant medications are allowed,especially the medcines which are not allowed before test ). Participants will be crossed-over to undergo another cough provocation test. Patient would be under observation in the out-patient clinics for \~2 hours following the cough provocation tests in case of severe adverse events. Twenty four hours after each test, a follow-up telephone visit will be scheduled for all patients to record any response which may be related to the test.
Study Type
OBSERVATIONAL
Enrollment
200
Adenosine Triphosphate aerosol
capsaicin aerosol
First Affiliated Hospital of Guangzhou Medical University
Guangzhou, Guangdong, China
RECRUITINGC5 (Provocant concentration eliciting at least 5 coughs)
Provocant concentration eliciting at least 5 coughs
Time frame: 18 months
ED50 (half maximal effective Dose)
50% effective dose of provocant
Time frame: 18 months
Emax (effective concentration of provocant eliciting maximal cough count)
effective concentration of provocant eliciting maximal cough count
Time frame: 18 months
potency ratio
ATP/capsaicin potency ratio
Time frame: 18 months
Difference in cough VAS score (a 10-point likert scale for assessing the global severity of cough, no subscale was applied)
The difference between pre- and post-challenge cough VAS scores
Time frame: 18 months
The incidence of adverse events (i.e. dry throat , pharyngeal itching)
adverse events such as dry throat , pharyngeal itching, wheeze or dyspnea according to the subject's reporting to record the rate of the incidence and the severity (the aboved-mentioned VAS score would be applied)
Time frame: 18 months
Cough dose ratio (CDR)
the ratio of cough count and dose/concentration
Time frame: 18 months
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