Drug-drug interactions (DDIs) are known to lead to treatment failure.

In most European countries there are no data on DDIs in patients within correctional facilities.

The main aim of this paper is to present the most frequent DDIs in the biggest Slovenian male, Slovenian correctional facility Dob to avoid serious DDIs in future.

A retrospective study was carried between September 2015 and June 2016 on 141 patients on substitution treatment (methadone, suboxone and buprenorphine) and 125 other prisoners with mental disorders in need for psychiatric treatment were included. All study data were extracted from the patients’ medical files of the psychiatric dispensary in the prison Dob. DDIs were determined by different interaction classes with Lexicomp Online™ 19.0 version and only X (major interactions and should be avoided) and D (minor interactions and avoid if it is possible) were included.

Together 220 patients were included. Number of patients with at least 1 interaction, were 139 (63.2%). Number of patients with at least 1 X interaction, were 59 (26.8%). Number of patients with more than one (1) X interactions was 15 (6.8%). More than half of the patients (56.4%) were treated by hypnotics and 38.4% with benzodiazepines. The most frequent X DDIs were: buprenorphine, methadone and sulpride with antipsychotics (clozapine and quetiapine) and antidepressants (e.g. escitalopram, fluoxetine).

In patients treated with methadone and buprenorphine there are frequent DDIs resulting in contraindications for prescribed combination of drugs. If an antidepressant is to be used in patients prescribed methadone and buprenorphine, sertraline is recommended.

The authors have not supplied their declaration of competing interest.