Drug–drug interactions (DDIs) between antibiotics and psychopharmaceuticals in large national data have not been described yet.

In most European countries, there is no national data on DDIs in patients within nursing homes.

To present the most important DDIs in the Slovenian nursing homes to avoid serious DDIs in the future.

A retrospective study was carried in 2015 and with 233 patient on antibiotic treatment. All study data from the patients’ records were obtained from the patients’ charts. DDIs were determined by different interaction classes with Lexicomp Online™ 19.0 version and only X (major interactions) and D (minor interactions) were included.

A total of 233 patients (age = 83.5, SD = 9.8) were treated with antibiotics (only 2 without psychopharmaceuticals). The number of patients with at least 1 interaction was: 72 (30.9%) for X and 172 (73.8%) for D and the average number of medication/patient was 10.9 (SD = 3.9). Twenty-seven patients (11.5%) were treated with at least 1 X DDIs s (17 patients ciprofloxacin, 6 moxifloxacin, 3 azithromycin and 1 levofloxacin). Quetiapine and ciprofloxacin was most frequent DDIs occured in 12 patients. Twenty-seven DDIs were pharmacodynamic (QTc prolongation) and 3 pharmacokinetic (ciprofloxacin-tizanidine, ciprofloxacin and duloxetine in 2 patients; n = 3). Quetiapine was most frequent prescribed psychopharmaceutical in X DDIs.

DDIs between these two groups are seen very often. If an antidepressant should be used in these patients, we recommend sertraline instead of escitalopram and venlafaxine instead of duloxetine and mirtazapine instead of quetiapine. We also recommend a use of penicilins instead of ciprofloxacin and azithromycin.

The authors have not supplied their declaration of competing interest.