Use of pro re nata medications in acute inpatient care

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.

The medical records of all patients admitted for >24h during a 2 month period were retrospectively audited for details regarding prescriptions and administrations of PRN medications.

A total of 420 records were reviewed, producing a total of 3868 PRN medication administrations. Ninety-seven per cent of all patients were prescribed PRN medications and 93.8% were prescribed regular medications. The most frequently prescribed medications were second-generation antipsychotics for regular use along with benzodiazepine for PRN use. Nearly 84% of patients received at least one PRN medication during their admission, while patients diagnosed with personality disorder received more PRNs per day. The most common reason for PRN administration was patient agitation. The results indicated poor documentation in the prescription and documentation of PRN administrations. Also, the findings show that a small subset of the patients (5%) received >30% of all PRN medications.

PRN medication use has endured as standard practice and the results of the present study are consistent with the reported frequency of use increasing slightly over the years. The combination of second-generation antipsychotics as regular medications and benzodiazepines for PRN medication is consistent with recommended treatment guidelines. The small subset of patients who were overrepresented in the PRN administrations is noteworthy.