OBJECTIVE: Opioid addiction is a disease that is increasing in our country, Turkey, and around the world, which it is difficult to treat in medical, social, and economic terms. Pregabalin is a preparation used for the treatment of epilepsy, neuropathic pain, and anxiety disorders. In opioid users, pregabalin is increasingly being self-administered off-label due to its euphoria effect at high doses. We investigated the effects of pregabalin on addiction profile and opioid withdrawal severity by comparing patients with opioid addiction who were and were not using off-label pregabalin. METHODS: Between July and August 2016, a total of 120 patients (60 patients were pregabalin users and 60 patients were non-users) who presented to Ankara Numune Training and Research Hospital Psychiatry Clinic Alcohol and Substance Addiction Treatment Center and were diagnosed with opioid use disorder according to the DSM-5, were included in the study. Patients who were using other substances were excluded from the study. A sociodemographic data form, the Clinical Opiate Withdrawal Scale, and Addiction Profile Index (API) were applied to the patients. RESULTS: There was no statistically significant difference between pregabalin users and pregabalin non-users in terms of age, sex, age of onset, working status, and whether previous treatment had been received. In the pregabalin user group, the severity of opioid withdrawal, API substance use characteristics, diagnosis, effects on life, craving, motivation subscale scores, and API total score were found to be significantly higher than in the nonuser group. CONCLUSION: Off-label pregabalin use among patients with opioid addiction is becoming more common. Off-label, high-dose pregabalin use may worsen existing opioid addiction, create a new area of addiction, and an illegal market. Highlights. We aimed to investigate the effects of pregabalin on addiction profile and opioid withdrawal severity by comparing patients with opioid addiction who were and were not using off-label pregabalin. . In the pregabalin user group, the severity of opioid withdrawal, and API total score were found to be significantly higher than in the non-user group. . The use of off-label, high-dose pregabalin may worsen existing opioid addiction. ARTICLE HISTORY