A Study of Ulonivirine (MK-8507) and Methadone in Healthy Volunteers (MK-8507-019)

Inclusion Criteria The main Inclusion Criteria include but are not limited to: * Is in good health * Has a body mass index (BMI) between \>18 and ≤40 kg/m\^2 * Is reliably participating in a methadone maintenance program for at least 2 months prior to Day 1 and is on a documented stable dose of methadone for at least 14 days prior to Day 1 Exclusion Criteria The main Exclusion Criteria include but are not limited to: * Has a history of cancer (malignancy) * Has a history of significant multiple and/or severe allergies, or has had an anaphylactic reaction or significant intolerability to prescription or nonprescription drugs or food * Has tested positive human immunodeficiency virus (HIV) or for a sexually transmitted infection at screening * Is under the age of legal consent