There is a paucity of research into PRN medication use in older psychiatric inpatients. This is an important topic given the risks of polypharmacy, adverse drug reactions, and high dose medication.

In 2013, we carried out a cross-sectional survey of the prescription and administration of sedative PRN medication to older adult inpatients on seven wards at a UK tertiary referral centre. We compared them with 242 patients of working age.

Of the 92 patients studied, 56 (60.9%) were prescribed PRN sedation and 25 (27.2%) had received one or more doses in the previous fortnight. In total, 70 doses had been administered; all by mouth and all but one as single doses. Lorazepam was by far the most commonly prescribed and administered PRN drug. Agitation was the main indication, although violence was the most commonly cited reason for administration but documentation of antecedents, non-pharmacological strategies and outcome including side effects was uniformly poor with only 37 (52.9%) doses recorded in the case notes. Those with organic disorders were just as likely to receive PRN as those with functional illnesses. Patients very rarely actually received high dose antipsychotics or antipsychotic polypharmacy as a result of PRN prescriptions. Older patients were less likely than adults of working age to be prescribed PRN and dosages were smaller.

Prospective studies of PRN prescription and administration are needed to better understand the reasons underpinning its use and to gain objective data upon its effectiveness or otherwise in this vulnerable patient group.