A Study to Evaluate the Effects of Multiple Doses of MK-1439 (Doravirine) on Pharmacokinetics of Methadone in Participants Requiring Methadone Maintenance Therapy (MK-1439-045)

Inclusion Criteria:

- If female with reproductive potential: must demonstrate a serum β-human chorionic
gonadotropin (β -hCG) level consistent with the nongravid state and agree to use
(and/or have their partner use) two acceptable methods of birth control throughout
the trial and until 2 weeks after the last dose of trial drug.

- If postmenopausal female: must be without menses for at least 1 year.

- If surgically sterile female: must have a status of post hysterectomy, oophorectomy
or tubal ligation.

- Body Mass Index (BMI) of 18-35 kg/m^2 (inclusive).

- Able to comply with the smoking restrictions, including <=10 cigarettes per day while
in the Clinical Research Unit, and no smoking from 2 hours predose to 2 hours
postdose on Days 1 and 6.

- Reliably participating in a methadone maintenance program for at least two months
prior to Day 1. Required to be on a documented stable dose of methadone for at least
14 days prior to Day 1.

- Agree not to change current maintenance methadone dose of 20-200 mg once daily
(unless for safety reasons) from screening until the end of the study. Must agree to
observation and documentation of daily methadone dose administration during the
period of the study during which they are domiciled.

Exclusion Criteria:

- Mentally or legally incapacitated, have significant emotional problems at the time of
pretrial (screening) visit or expected during the conduct of the trial or have a
history of clinically significant psychiatric disorder of the last 5 years.
Participants who have had situational depression may be enrolled in the trial at the
discretion of the investigator.

- History of clinically significant endocrine, gastrointestinal, cardiovascular,
hematological, hepatic, immunological, renal, respiratory, genitourinary or major
neurological (including stroke and chronic seizures) abnormalities or diseases.
Participants with a history of uncomplicated kidney stones or childhood asthma may be
enrolled in the trial at the discretion of the investigator.

- History of cancer (malignancy) - exceptions apply.

- History of significant multiple and/or severe allergies (e.g. food, drug, latex
allergy), or has had an anaphylactic reaction or significant intolerability to
prescription or non-prescription drugs or food.

- Positive for Human Immunodeficiency Virus (HIV).

- Major surgery, donated or lost 1 unit of blood (approximately 500 mL) within 4 weeks
prior to the pretrial (screening) visit.

- Participated in another investigational trial within 4 weeks prior to the pretrial
(screening) visit.

- Nursing mother.

- Unable to refrain from or anticipates the use of any medication, including
prescription and non-prescription drugs or herbal remedies beginning approximately 2
weeks prior to the first dose of the 14 day methadone maintenance phase prior to Day
1, throughout the trial, until the post-trial visit - exceptions apply.

- Consumes greater than 3 glasses of alcoholic beverages (1 glass is approximately
equivalent to: beer [354 mL/12 ounces], wine [118 mL/4 ounces], or distilled spirits
[29.5 mL/1 ounce]) per day - exceptions apply.

- Consumes excessive amounts of caffeine, defined as greater than 6 servings (1 serving
is approximately equivalent to 120 mg of caffeine) of coffee, tea, cola,
energy-drinks, or other caffeinated beverages per day.

- Has a positive screen for drugs with a high potential for abuse such as cocaine,
amphetamines, methylenedioxymethamphetamine (MDMA), barbiturates, benzodiazepines
(exceptions apply), or opiates/opioids (apart from methadone as assigned maintenance
therapy) on Day 1 that cannot be explained by concomitant medications, unless at the
discretion of the principal investigator and the sponsor. Must have a negative Urine
Drug Screen prior to randomization, with the exception of tetrahydrocannabinol (THC)
and prescription benzodiazepines.

- Clinical Opiate Withdrawal Scale (COWS) score of >=5 prior to randomization.