Comparison of Standard Opioid Prescription Versus Prescription Guided by Pharmacogenetic Analysis in Patients With Non-cancerous Chronic Pain.

Inclusion Criteria: * The patient must have given their free and informed consent and signed the consent form * The patient must be a member or beneficiary of a health insurance plan * The patient is at least 18 years old * The patient will be available for all visits * Patients suffer from non-cancerous chronic pain according to HAS criteria * Patient not having taking opioids in previous 2 months * Patient indicated for prescription of opioids (oxycodone, codeine or tramadol) or patient not responding to first line treatment Exclusion Criteria: * The subject is participating in an category I interventional study, or is in a period of exclusion determined by a previous study * The subject refuses to sign the consent * It is impossible to give the subject informed information * The patient is under safeguard of justice or state guardianship * The patient is pregnant or breastfeeding * The patient is likely to procreate and does not use an effective method of contraception (contraceptive ring, surgical contraception, implant, patch, contraceptive pill, male and female condoms, IUD) * There is a contra-indication for opioid use * Patient with an addiction risk (score ≥ 8 on ORT scale).