Limited evidence for the effectiveness of p.r.n. Medications among psychiatric inpatients.

The use of medications on a p.r.n. basis on psychiatric inpatient wards is common and widespread but without clear evidence of effectiveness. While individual studies have explored the use of p.r.n. medications in patients receiving scheduled psychotropic medications, no systematic review of the effectiveness of this use of p.r.n. medications has been done. A MEDLINE search was performed of all articles published in English between 1966 and November 2008. Studies were included only if they involved psychiatric patients and if they quantitatively explored the effectiveness of p.r.n. medications. Ten retrospective studies were identified that met inclusion criteria. Among the studies involving adult inpatients, estimates of effectiveness, primarily in the management of agitation, were consistently moderately high, averaging approximately 75%. These studies mainly involved use of antipsychotics and benzodiazepines. Lower estimates of about 30% were obtained in studies involving non-adult inpatients who had few psychotic disorders and among whom there was only minimal use of p.r.n. benzodiazepines. The meaning of effectiveness was often unclear across these retrospective studies. It also appears that important outcome measures, such as duration of hospitalization, may not be affected. Administration of p.r.n. medication was also associated with a greater risk of adverse events. Future studies concerning use of p.r.n. medications in psychiatric patients should examine objective ratings of agitation, medication effects, and adverse events.