Effect of Gefapixant (MK-7264/AF-219) on Cough Reflex Sensitivity in Healthy and Chronic Cough Participants (MK-7264-014)

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 kg/m\^2; * 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; * Be non-smokers for at least 5 years; * If a female of child-bearing potential (I. e., have not undergone a hysterectomy or bilateral oophorectomy) or not post-menopausal (defined as no menses for at least 12 months), agree to use 2 forms of acceptable birth control; or if a male, they and/or their partner of child-bearing potential agree to use 2 forms of acceptable birth control; * Be able to communicate effectively with the Investigator and other study center personnel and agree to comply with the study procedures and restrictions. * Subjects with chronic cough must have treatment-refractory chronic cough for at least one year, with no objective evidence of an underlying trigger (e. g., asthma) Exclusion Criteria: * History of upper respiratory tract infection or recent significant change in pulmonary status within 4 weeks of the Baseline Visit (Day 0); * Have acute worsening of asthma; * Do not cough during the ATP or Capsaicin or Citric acid challenge at Screening or only cough twice…