Conditions: Refractory Chronic Cough
Allocation: RANDOMIZED | Intervention model: CROSSOVER
Enrollment: 36
Healthy volunteers: yes

Brief summary:
The primary objective of this study was to assess the effect of a single dose of gefapixant 100 mg on cough reflex sensitivity to various challenge agents (capsaicin, citric acid, adenosine triphosphate \[ATP\], and distilled water) in healthy and chronic cough participants.

Detailed description:
The study had a Screening period to determine participant inclusion, two Baseline Visits, and two treatment periods with a minimum 48-hour washout between the treatment periods. At Baseline and during each treatment period, cough sensitivity was measured by standard clinical methodology incorporating four cough challenges. Daytime cough monitoring was performed at Baseline and during each of the two treatment periods (chronic cough participants only).

Arms:
arm 1: Healthy participants in Sequence A received a single dose of placebo in treatment Period 1 then a single dose of gefapixant 100 mg in treatment Period 2. There was a minimum 48-hr washout between Periods 1 \& 2. arm 2: Healthy participants in Sequence B received a single dose of gefapixant 100 mg in treatment Period 1 then a single dose of placebo in treatment Period 2. There was a minimum 48-hr washout between Periods 1 \& 2. arm 3: Chronic Cough participants in Sequence A received a single dose of placebo in treatment Period 1 then a single dose of gefapixant 100 mg in treatment Period 2. There was a minimum 48-hr washout between Periods 1 \& 2. arm 4: Chronic Cough participants in Sequence B received a single dose of gefapixant 100 mg in treatment Period 1 then a single dose of placebo in treatment Period 2. There was a minimum 48-hr washout between Periods 1 \& 2.

Interventions: intervention 1: Gefapixant 100 mg intervention 2: Placebo
Intervention descriptions: intervention 1: Gefapixant 100 mg (2 x 50 mg tablets), administered orally as a single dose in treatment Period 1 or treatment Period 2 intervention 2: Placebo (two tablets matching gefapixant 50 mg), administered orally as a single dose in treatment Period 1 or treatment Period 2

Protocol document: