Preference for Subutex® (Buprenorphine) Versus Suboxone® (Buprenorphine/Naloxone) in Opioid Dependent Patients on Subutex® (Study P05094)(COMPLETED)

Inclusion Criteria: * Subject must demonstrate their willingness to participate in the study and comply with its procedures by signing a written informed consent. * Subject must be at least (\>=) 18 years of age, of either sex. * Subject treated for opioid dependence with Subutex® with a stable daily dose between 2 mg and 16 mg daily, for at least 6 months. * Subject who do not inject/misuse their treatment with Subutex®. * Subject must be free of illicit opiate drug use as assessed by urine test performed prior to inclusion. * Subject 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: * Subject not eligible for treatment with Subutex® or Suboxone® according to the legal drug attachments. * Subject refusing to take the daily dose of the study medication under control in the center. * Subject unable to complete the evaluations. * Women who are pregnant or nursing. * Subject with a history of hypersensitivity to buprenorphine hydrochloride or naloxone hydrochloride dihydrate or any excipient of Subutex® or Suboxone®. * Subject with a current evidence of alcohol abuse. * Subject with severe respiratory dysfunction, severe hepatic dysfunction, acute alcohol intoxication or delirium tremens . * Subject with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucosegalactose malabsorption. * 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 and monoamine oxidase \[MAO\] inhibitors, * CYP3A4 inhibitors, * CYP3A4 inducers. * Subjects 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 subject safety. * Subjects who have used any investigational product within 30 days prior to enrollment. * Subjects participating in another trial at the same time. * Subject who intend to donate blood during the study or within 3 months after study completion. * Subjects in the exclusion period of the "Fichier National des Personnes qui se Prêtent à des Recherches Biomédicales" (National Index of Persons Participating in Biomedical Researches, or National Index of Volunteers).