Effect of Gefapixant (AF-219/MK-7264) on Cough Reflex Sensitivity (MK-7264-015)

Inclusion Criteria: * Have provided written informed voluntary consent; * Be able to speak, read, and understand English; * Be males or females, of any race, between 18 and 80 years of age, inclusive; * Have a body mass index (BMI) ≥18 and \<35.0 kg/m2; * Be in good general health with no clinically relevant abnormalities based on the medical history, physical examination, clinical laboratory evaluations (hematology, clinical chemistry, and urinalysis), and 12 lead electrocardiogram; * Women of child bearing potential must have a negative pregnancy test at Screening and prior to randomization. * Women of child-bearing potential must use 2 methods of acceptable birth control from Screening until 3 months after the last dose of study drug; * Male subjects with partners of child-bearing potential (as defined in Inclusion No. 8) must use 2 methods of acceptable birth control, 1 of which must be a barrier method; * Subjects with chronic cough * Be able to communicate effectively with the Investigator and other study center personnel and agree to comply with the study procedures and restrictions Exclusion Criteria: * Current smoker; * Individuals who have given up smoking within the past 6 months, or those with \>20 pack-year smoking history(chronic cough subjects), or \>10 pack-year smoking history (healthy subjects); * History of upper respiratory tract infection or recent significant change in pulmonary status within 4 weeks prior to Screening or prior to randomization; * His…