This is a randomized, double blind, placebo controlled study in opioid dependent subjects. Subjects meeting entry criteria will be treated with multiple doses of B-BNX or B-Placebo, with non-responders rescued within 6 hours. Open treatment B-BNX will be administered as follow-up therapy. Clinical efficacy assessments include the clinical opioid withdrawal scale (COWS), subject-rated assessments, and a urine drug screen.