Efficacy Study to Evaluate Buprenorphine HCl Buccal Film in Opioid-Experienced Subjects

Inclusion Criteria: * Diagnosis of moderate to severe low back pain for ≥6 months * Treating CLBP with a stable daily maintenance dose of ATC opioid analgesic medication equivalent to ≥30 mg and ≤160 mg morphine sulfate equivalents (MSE) per day for ≥4 weeks. (Additional as needed \[PRN\] analgesic rescue medications permitted on top of the stable daily maintenance dose of ≥30 mg MSE opioid analgesic, but must be included in the total daily MSE calculation and in combination with the stable daily maintenance dose not to exceed 160 mg MSE per day) * Stable health, as determine by Principal Investigator * Females are practicing abstinence, using a medically acceptable form of contraception, or post-menopausal, biologically sterile, or surgically sterile for more than 1 year * Willing and able to comply with all protocol required visits and assessments Exclusion Criteria: * Current cancer related pain or received chemotherapy within 6 months of screening * Subjects with history of other chronic painful conditions * Reflex sympathetic dystrophy or causalgia, acute spinal cord compression, cauda equina compression, acute nerve root compression, meningitis, or discitis * Allergy or contraindications of any opioid or acetaminophen * Surgical procedure for relief of pain within 6 months * Hypokalemia or clinically unstable cardiac disease, including: unstable atrial fibrillation, symptomatic bradycardia, unstable congestive heart failure, or active myocardial ischemia * QT interval corrected using Fridericia's formula (QTcF) of ≥450 milliseconds on the 12-lead electrocardiogram (ECG) * History of long QT syndrome or a family member with this condition * Moderate to severe hepatic impairment * Moderate to severe renal impairment * Current or past history of alcohol abuse * Positive urine toxicology screen for drug of abuse * History or abnormalities on physical exam, vital signs, electrocardiogram, or laboratory values