High-dose benzodiazepine (BDZs) represents an important risk factor for dependence, particularly in a prison environment. In Lyon's prison, BDZs and/or opioid maintenance treatment are often prescribed to patients with mental disorders. The aim of this retrospective study was to assess the impact of psychiatrist and pharmacist collaboration on reducing the BDZs dose prescribed to prisoner patients. Since 2001, clinicians and pharmacists have been holding monthly meetings to develop prescribing guidelines and discuss those patients receiving high-dose BDZs. All prescribed psychotropic drugs were noted for each included patient in the control (before guidelines) and intervention groups. Criteria used to define each patient profile included age, diagnosis (mental disorder), and concomitant treatment (opioids, antidepressants). To compare each group, the daily dose of prescribed BDZs was used as a quantitative variable and expressed in diazepam equivalent. Four hundred and seventy-three patients were included, 222 in the control group and 251 in the intervention group. The two groups showed no difference in terms of diagnosis. The daily dose of BDZ was higher in the control group when all patients were considered (meanCONTROL GROUP = 46 mg in diazepam equivalent vs. meanINTERVENTIION GROUP = 34 mg) and for each of the following patient categories: ‘mental disorder' (48 mg vs. 30 mg), ‘no opioid treatment' (44 mg vs. 31 mg), ‘buprenorphin treatment' (58 mg vs. 63 mg), ‘no antidepressant treatment' (41 mg vs. 29 mg), and ‘antidepressant treatment' (53 mg vs. 38 mg). The results of this retrospective study show the positive impact of multidisciplinary intervention on reducing the prescribed daily dose of BDZs. This experience confirms the positive impact that pharmacist feedback on prescriptions and the development of treatment guidelines by clinician and pharmacist collaboration have on improving the prescribing practice in a prison environment.