Table 1.

Summary for the comparisons of findings between the studies.

Title	Year of Publication	Country	Aim	Participants	Methods	Findings for the Main Comparison *
						Outcome	Impact	Agreement between Studies
Effect of acetaminophen on behaviour, well-being and psychotropic medication use in nursing home residents with moderate-to-severe dementia [29]	2005	USA	To evaluate the effect of regularly scheduled administration of analgesic medication compared with analgesia ‘as needed’ on behaviour, emotional well-being and use of as-needed psychotropic medications in nursing home residents with moderate-to-severe dementia.	25 nursing home residents in two nursing homes, 3 male and 22 females, with a mean age of 85.9 ± 7.4	Randomized, double-blind, placebo-controlled, crossover trial.	Psychological effects	No effect was reported on emotional well-being, agitation or quality of life.	High
						Appropriateness of prescription and administration	The frequency of psychotropic use by routine and PRN administration did not differ between study arms and phases.	High to moderate
						Adverse events	Some adverse events unrelated to the medication and drug use pattern were reported.	High to moderate
The impact of a good practice manual on professional practice associated with psychotropic PRN in acute mental health wards: an exploratory study [15]	2008	UK	To assess the effect and acceptability of a good practice manual on prescribing and administration practices of PRN psychotropic medication in acute mental health wards.	12 physicians, 11 nurses and 35 patients in two acute mental health wards; gender and age of participants were not reported.	Pre-post exploratory design. Methods of sampling and patient selection were not reported	Appropriateness of prescription and administration	The practice manual influenced the administration and prescription of PRN medication. The prescription and administration of benzodiazepines and antipsychotics were reduced, whilst the z-drugs were increased. The maximum doses of antipsychotics administered using PRN prescriptions were above safety limits stated in the British National Formulary. Patient education and provision of information were increased. Inappropriate or excessive doses, duplicated co-prescriptions, administration errors and problematic documentation were reported in both arms.	High to moderate
The efficacy of intravenous patient-controlled analgesia after intracranial surgery of the posterior fossa: a prospective, randomized controlled trial [30]	2012	USA	To investigate whether IV patient-controlled analgesia (PCA) would lead to reductions in postoperative pain after neurosurgical procedures involving the posterior fossa compared with conventional IV nurse-administered as-needed (PRN) therapy.	80 patients undergoing elective surgery in the neurology critical care unit. The male/female distributions were 31/21 and 11/20 and the mean ages were 41.4 ± 11.1 years and 45.4 ± 14.6 years for two study arms.	Block randomized controlled trial	Appropriateness of prescription and administration	Patients in the PCA arm received more analgesia and had more pain relief than the PRN arm	High to moderate
						Physical effects	Patients in the PCA group reported less severe pain than the PRN group.	High
						Adverse events	Some adverse events unrelated to the medication and drug use pattern were reported.	High to moderate
Naproxen twice daily versus as needed (PRN) dosing: efficacy and tolerability for treatment of acute ankle sprain, a randomized clinical trial [31]	2013	Iran	To compare the efficacy and safety of naproxen 500 mg twice daily (bd) versus naproxen 500 mg as needed (PRN) for treatment of ankle sprain.	135 patients with ankle sprain presenting at the emergency department of a teaching hospital. Mean ages were 29.8 ± 10.7 years and 34.08 ± 15.07 years and gender distribution was 40 (64.5%) and 33 (55%) for male in the study arms.	Block randomized, parallel group trial	Appropriateness of prescription and administration	Adherence to therapeutic regimen was higher in the bd arm but there was no difference in analgesic effectiveness.	High to moderate
						Physical effects	Overall pain reduction was unaffected by mode of prescription.	High
						Adverse events	PRN regimens appeared safer than the twice daily regime, possibly due to a significant lower consumption in the number of tablets.	High to moderate
Comparison of the efficacy and safety of once-daily dosing and on-demand use of udenafil for type 2 diabetic patients with erectile dysfunction [32]	2015	South Korea	To compare the efficacy and safety of once-daily dosing with on-demand use of udenafil for type 2 diabetic patients with erectile dysfunction (ED).	141 patients with type 2 diabetes in seven healthcare centres.The sample was all male with the mean ages of 54.44 ± 6.00 years and 53.88 ± 6.07 years in the study arms.	Randomized, open-label, parallel-group	Physical effects	No differences in efficacy or biomarkers of endothelial function were identified.	High
						Adverse events	No significant difference was found between once-daily and PRN dosing with regard to treatment-related adverse drug reactions.	High to moderate

* Population: Older people, patients, healthcare providers. Interventions: PRN drug use and comparison with other types of drug use patterns.