Study of Two Formulations of Buprenorphine HCl in Opioid-dependent Subjects on Buprenorphine Maintenance Therapy (Study P04451) (COMPLETED)

Inclusion Criteria: * Patients must demonstrate their willingness to participate in the study and comply with its procedures by signing a written informed consent. * Patients must be at least (≥) 18 years of age, of either sex. * Patients treated for opioid dependence with Subutex®, with a stable dosage of 8 mg or 16 mg daily, and respecting the legal drug attachments. * Patients must understand and be able to adhere to the dosing and visit schedules, and agree to report concomitant medications / products and adverse events to the investigator or designee. * Women of childbearing potential (includes women who are less than one year postmenopausal and women who become sexually active) must be using or agree to use an acceptable method of birth control (e.g., hormonal contraceptive, medically prescribed IUD, condom in combination with spermicide) or be surgically sterile (e.g., hysterectomy or tubal ligation). * Women of childbearing potential should be counseled in the appropriate use of birth control while in this study. Women who are not currently sexually active must agree and consent to use one of the above-mentioned methods should they become sexually active while participating in the study. * Women of childbearing potential must have a urine pregnancy test with negative result within 2 weeks prior to inclusion (as performed under control of the investigator or designee). Exclusion Criteria: * Patients refusing to take the daily dose of the study medication under control in the center. * Patients unable to complete the evaluations. * Women who are pregnant or nursing. * Patients with a history of hypersensitivity to buprenorphine hydrochloride or any excipient of one of its formulations. * Patients with a current evidence of alcohol abuse. * Patients with severe respiratory dysfunction, severe hepatic dysfunction, acute alcohol intoxication or delirium tremens. * Initiation or increase in the dose, within the past 7 days or scheduled during the study, of a treatment with: * benzodiazepines, * other depressants of the central nervous system: other morphine derivatives (analgesics, antitussives), certain antidepressive agents, sedative H1 antihistamines, barbiturates, benzodiazepines, anxiolytics other than benzodiazepines, neuroleptics, clonidine and clonidine-like agents, * monoamine oxydase \[MAO\] inhibitors. * Patients who have any current evidence of clinically significant hematopoietic, metabolic, cardiovascular, immunologic, neurologic, hematological, gastrointestinal, hepatic, renal, psychiatric, cerebrovascular, or respiratory disease, or any other disorder which, in the judgment of the investigator, may interfere with the study evaluations or affect patient safety. * Patients who have used any investigational product within 30 days prior to enrollment. * Patients participating in another trial at the same time. * Patients intending to donate blood during the study or within 3 months after study completion. * Patients in the exclusion period of the "Fichier National des personnes qui se prêtent à des recherches biomédicales sans bénéfice individuel direct" (National Index of persons participating in biomedical researches without direct individual benefit, or National Index of volunteers). * Patients without Social Security number, or whose maximum annual compensation (3,800 €) has been exceeded.