The purpose of the study was to assess the efficacy of induction treatment with buprenorphine/naloxone (BNX) sublingual tablet s compared with induction treatment with buprenorphine only. The hypothesis is that starting directly on OX219 works equally well (e.g. not significantly worse) as starting on buprenorphine only and switching to OX219 on Day 3.

This was a prospective, randomized, multicenter, blinded, parallel-group, active-controlled, non-inferiority study conducted at 13 sites within the US. Eligible patients participated in 8 treatment visits on Days 1, 2, 3, 4, 8, 15, 22, and 29. Effectiveness of treatment was assessed as follows:

• Retention in treatment at Day 3
• Clinician and patient assessments of opioid withdrawal symptoms
• Assessment opioid cravings

Inclusion Criteria:

• Able to read, comprehend, and sign the informed consent form and willingly provide written informed consent
• Prepared to engage in opioid replacement therapy and to abstain from opioid utilization other than the study drug, and from other illicit drugs
• Male or female, 18 to 65 years of age (inclusive)
• Met clinical criteria for opioid dependence in past 12 months based on DSM-IV-TR
• Provided buprenorphine-negative urine drug screen prior to randomization
• Provided negative urine pregnancy test
• Females of childbearing potential were required to be using a reliable method of contraception (e.g., hormonal, condom with spermicide, intrauterine device [IUD]) after the screening visit and for the duration of the study
• Participants receiving opioids for pain must receive clearance from their prescribing physician to be withdrawn from their prescribed opioids
• Generally good health as determined by the investigator
• Participants should demonstrate at least mild withdrawal symptoms (defined as a COWS score >9 at Day 1 predose)

Exclusion Criteria:

• Females who are pregnant or lactating, or planning to be pregnant during study
• Any previous prescribed treatment with buprenorphine monotherapy (e.g., generic buprenorphine sublingual tablets)
• Prescribed treatment with buprenorphine or naloxone within 90 days prior to start of treatment
• Methadone patients with any daily dose over 30 mg during the past week and who received the last dose of methadone less than 30 hours prior to start of treatment
• Participants who are unwilling or unable to comply with the requirements of the protocol
• Participants who are participating in any other clinical study in which medication(s) are being delivered or who have used an investigational drug or device within the last 30 days
• Participants with any known allergy or sensitivity or intolerance to buprenorphine, naloxone, or any related drug
• Participants who are on the staff, affiliated with, or a family member of the staff personnel directly involved with this study
• Participants with serious untreated Axis I DSM-IV-TR psychiatric comorbidity
• Tongue piercing or other piercings in the mouth, including lips and cheek
• Participants with current or history of clinically significant medical disorder or condition
• Participants who are human immunodeficiency virus (HIV)-seropositive with a CD4+ count <200 or active acquired immune deficiency syndrome (AIDS)
• Participants who have any Class III or IV congestive heart failure, symptomatic myocardial ischemia, a history of long QT syndrome.
• Participants who are currently taking Class 1A antiarrhythmic medications or Class III antiarrhythmic medications
• Participants who have uncontrolled hypertension or clinically significant ECG abnormalities
• Participants who have a pulse oximetry ≤93% at screening, due to any medical reason.
• Individuals with AST or ALT levels ≥3 X the upper limit of normal or total bilirubin or creatinine ≥1.5 X ULN, on the screening laboratory assessments
• Participants with known significant liver disease.
• Participants who take any medication, nutraceutical, herbal product with known CYP3A4 inhibition or induction properties within 14 days of screening.
• Participants who are at suicidal risk