Introduction The objective of this study was to assess the reliability of drug–drug interaction software in monitoring prescriptions in psychiatric settings.

Method A 1 day cross sectional analysis of the ongoing drug regimens in the inpatient population was carried out.

Results This study showed a relatively high prevalence of hazardous or contraindicated drug combinations (approximately 15%). Three major categories of interactions were found: (1) those requiring diagnostic tests; (2) those requiring dosage adjustments, an appropriate drug choice or pharmacological class; and (3) those whose risk–benefit ratio was positive in the treatment indication.

Discussion The findings demonstrate that without access to biological test results and indications, the most prevalent interactions cannot be validated by the pharmacist. These results suggest that the availability of these data is essential, and that interactions with prescribers should be facilitated in order to increase the quality of clinical pharmacy in psychiatry.