Use of pro re nata medications in acute inpatient care.

Objectives: Available evidence suggests that the use of 'as needed' (PRN; from the Latin pro re nata: for an occasion that has arisen) medications has remained a standard aspect of treatment in acute inpatient mental health units over a number of years despite lack of evidence from controlled clinical trials. The practice is one in which doctors and nurses are interdependent; that is, while doctors prescribe the medications, professional nurses are the ones who make the clinical decisions to administer them. The aim of the present study was to provide a detailed description of the circumstances surrounding the use of PRN medications across four inpatient units in Sydney.