Long-term use of opioids for chronic pain is a growing health and social problem, mainly because of the risk of dependence. Buprenorphine/naloxone is used as substitution therapy for opioid dependence. This substitution therapy in patients with opioid dependence lessens withdrawal symptoms and craving. There is limited research on the effectiveness of buprenorphine/naloxone in patients with chronic pain and iatrogenic opioid dependence. The primary aim of this study is to investigate the effectiveness of buprenorphine/naloxone in patients suffering from chronic pain and an iatrogenic induced dependence on opioids. This study will investigate the effects of opioid substitution by buprenorphine/naloxone in patients suffering from chronic pain using long-term opioids, with pain and withdrawal symptoms as primary outcome measures. Secondary outcome measures will be craving, substance use, psychiatric comorbidity and quality of life.

This is a prospective open-label observational cohort study (exploratory pilot). Investigators will include 20 patients between 18 and 65 years with chronic pain and dependence on opioids, who were referred by their physician for replacement of opioids to buprenorphine/naloxone. Exclusion criteria are contraindications for buprenorphine/naloxone and patients with psychiatric disorders requiring acute treatment. The degree of pain and withdrawal symptoms will be assessed by the Quantitative Sensory Testing (QST) measurement and the following questionnaires: Visual Analog Scale (VAS), Objective Withdrawal Scale (OWS) and Subjective Withdrawal Scale (SWS). Secondary, craving and substance use/degree of opioid dependence will be studied using the Current Opioid Misuse Measure (COMM) and Obsessive Compulsive Drug using Scale (OCDS). Psychiatric comorbidity will be assessed using the following questionnaires: Depression, Anxiety and Stress Scale (DASS), Personality Inventory for DSM-5 (PID 5-BF), The 20-item Toronto Alexithymia Scale (TAS-20), Inventory of Depressive Symptomatology (IDS), the Perseverative Thinking Questionnaire (PTQ) and Mini International Neuropsychiatric Interview (MINI). These questionnaires are part of the standard assessment at the department of psychiatry at the Radboud University Medical Centre, Nijmegen. The EuroQol five dimensions questionnaire (EQ5D) will be used to assess the quality of life. During the replacement of opioids to buprenorphine/naloxone, the buprenorphine/naloxone protocol will be used.

Inclusion Criteria:

• Adult men and women aged 18 to 65 years
• suffering from chronic pain (pain for more than 6 months)
• iatrogenic opioid dependence (according to the DSM-5 criteria)
• there is informed consent for using the data for scientific analyses.

Exclusion Criteria:

• Contraindications for buprenorphine/naloxone, such as severe respiratory insufficiency, severe hepatic insufficiency, alcohol intoxication or delirium tremens.
• In addition participants with psychiatric disorders requiring acute treatment will be excluded, for instance an acute psychosis, acute manic episode or patients who are suicidal.

Adult men and women aged 18 to 65 years suffering from chronic pain (pain for more than 6 months) and iatrogenic opioid dependence (according to the DSM-5 criteria).