Table 3.

Prevalence and type of PRN prescription and administration.

Authors/Year	Prevalence of PRN Prescription	Prevalence of PRN Administration	Medicines Prescribed or Administered PRN
Snowdon et al., 2011 [37]	Mean number of 1.3 per resident Mean number of 0.9 when topical applications such as ear, eye, nose, and dermatological preparations were excluded (no measures of dispersion reported.)	Once or more in every 5 prescriptions	Clonazepam and midazolam for six residents and antipsychotic and/or anxiolytic medications including haloperidol to 3.3% of residents and Risperidone to 1%. Numerators and denominators were not reported.
Carder, 2012 [38]	Nearly all residents had a PRN order, with a range from 0 to 14 per resident, and with a mean of 5.82 (no measures of dispersion reported.)	No data	No data
Rønningen et al., 2013 [39]	1.1% (n = 183) of prescriptions	519 of the 839 (61.9%)	Psychotropic medications such as oxazepam, clomethiazole, diazepam, zopiclone, tramadol, morphine, and oxycodone were among the most frequently prescribed and administered medications as different brand names or pharmaceutical formulations (e.g., tablets and suppositories). Percentages, numerators, and denominators were not reported.
Voyer et al., 2015 [40]	19.9% of prescriptions	No data	Antipsychotics including risperidone (37.9%), haloperidol (34.5%), quetiapine (10.3%), olanzapine (10.3%), haloperidol, and quetiapine (3.4%) were prescribed. After 5 months, olanzapine was replaced by risperidone (3.4%). Numerators and denominators were not reported.
Dörks et al., 2016 [41]	A total of 2117 (27.9 %) prescriptions were PRN. Additionally, 638 (74.9 %) received at least one PRN medication. Each resident was treated with a mean of 2.5 ± 2.3 PRN medications.	No data	Lorazepam was prescribed to 67 (7.9%) of residents with a mean duration of 579 ± 627 days.
Allers et al., 2017 [42]	A percentage of 35.9% of prescriptions to residents with dementia vs. 23.0% for those without dementia were PRN.	No data	23.8% of residents with dementia and 5.7% without dementia were prescribed PRN antipsychotics. Only a small percentage of residents without dementia received PRN antipsychotics alone, without any scheduled antipsychotic medications (3.1%), a lower proportion than residents with dementia (10.8%). Residents with dementia were prescribed both scheduled and PRN antipsychotics more often than residents without dementia (13.0 vs. 2.5%). Of typical antipsychotics, melperone and promethazine were most often prescribed. Numerators and denominators were not reported.
Westbury et al., 2018 [43]	PRN antipsychotics were prescribed to 10.8% (9.5-12.1%) and benzodiazepines to 30.1% (27.6-32.6%) of residents.	No data	Antipsychotics, excluding lithium and prochlorperazine, and all types of benzodiazepines were converted to diazepam equivalents, but no separate data on each medication were provided.
Westbury et al., 2019 [44]	Of 11368 residents, 1261 (11.1%) and 3461 (30.5%) were prescribed PRN antipsychotics and PRN benzodiazepines, respectively.	No data	A percentage of 11.1% of residents were prescribed PRN atypical antipsychotics, including risperidone, quetiapine, and olanzapine, and typical antipsychotics such as haloperidol. Benzodiazepine, as an anxiolytic, prescribing included oxazepam, diazepam, and alprazolam to 17.9% of residents. Hypnotics, temazepam, and nitrazepam were prescribed to 16.4%. Both regular and PRN benzodiazepines were prescribed to 1150 residents (47%). Additionally, 724 (29%) of them with regular antipsychotic orders were prescribed extra doses of PRN.

PRN: pro re nata.