AbstractPro re nata (PRN), a Latin phrase meaning ‘as needed’, is used to describe medications that might be used in specific situations, in addition to regularly‐scheduled medications, such as when a patient is particularly anxious, experiencing insomnia, or suffering pain. While helpful in some circumstances, PRN are associated with an increased risk of morbidity, overuse, dependence, and polypharmacy. There is also a dearth of medical literature describing current practices and trends of PRN administration in mental health facilities, especially in Canada, and the literature that does exist is limited by poor documentation practices. Therefore, the primary objective of the current study was to understand the reason (purpose), frequency, use, documentation practices, and outcome (i.e. effectiveness, side‐effects) of PRN medication use on inpatient units. Data were pulled to capture a snapshot of PRN administrations over a 3‐month period, and included information related to the administration of the PRN medication, such as time of administration, type and dose of PRN medication, and prescribed indication, as well as patient‐specific information. Results indicated that approximately 8200 psychotropic PRN medications were administered during the designated 3‐month time period, and over 90% of patients received at least one PRN. Most of these were benzodiazepines, followed by antipsychotics. Further analyses were conducted to determine other characteristics of PRN use patterns and to provide a baseline of understanding that will inform future research to investigate the practice of PRN administration to psychiatric inpatients.