All patients with moderate or severe OUD diagnosis (according to Diagnostic and Statistical Manual Diploma in Social Medicine 5) who initiate OMT in addictionology department of Nantes hospital or in addiction care and prevention centers of Nantes could be included. Data will be collected during 3 visits.
During the first visit (inclusion), clinical interview, electrocardiogram, urinary and blood tests (pharmacokinetics and pharmacogenetics analysis) will be provided. Infectious disease screening and fibroscan could be also provided as the patient wishes. Inclusion visit will also correspond to initiation of OMT.
At 6 months follow-up (second visit) clinical interview, electrocardiogram, urinary and blood tests (pharmacokinetics and pharmacogenetics analysis) will be provided.
At 12 months follow-up (final visit) clinical interview, electrocardiogram and urinary test will be provided.