The use of PRN or 'as required' medication by mental health nurses is an important, yet little explored aspect of psychiatric inpatient care. In a survey of 100 inpatients in Canada (Craven et al. 1987), it was reported that 88% had been prescribed PRN medication. The most frequently administered drugs were antipsychotics, anticholinergics, and benzodiazepines. Similar results were found in a study by Walker (1991). Craven et al. (1987) also highlight that people over the age of 50 are more likely to be given PRN medication, and suggest that gender and legal status do not influence administration. Vitello et al. (1991), in a study of factors affecting the administration of PRN medication on a children's psychiatric unit, demonstrated that 91% of administrations were given orally (compared to 9% via intramuscular injection); however it is unclear if this finding can be generalized to an adult psychiatric setting. Mental health nurses' reasons for administering PRN medication have not been examined.