Kenkyu Journal of Pharmacy Practice & Health Care ISSN : 2455-4421
Use of PRN medications at an academic medical facility: Observational analysis
  • Christina DeRemer* ,

    Internal Medicine Clinical Pharmacist & Medicine Team Supervisor Georgia Regents Medical Center, 1120 15th Street, BI-2101, Augusta, GA 30912, Tel: 706-721-0798; Fax: 706-721-9138, e-mail: cderemer@gru.edu

  • Jacquelyn Bryant ,

    Critical Care Specialty Pharmacist, Georgia Regents Medical Center, Augusta, GA 30912, USA

  • Lee Merchen ,

    Program Director of Internal Residency Program, Medical College of Georgia, USA

Received: 11-12-2015

Accepted: 21-12-2015

Published: 28-12-2015

Citation: Christina DeRemer, Jacquelyn Bryant, Lee Merchen, et al. (2015) Use of PRN medications at an academic medical facility: Observational analysis. Pharma Health Care 1: 100106

Copyrights: © 2015 Christina DeRemer, et al.


Introduction: Inclusion of “as needed,” PRN, or anticipatory medication orders have become an accepted prescribing tactic across varying medical areas. Accompanying this practice are concerns for interpretation of intent for medications and safety due to overuse, interactions, or misinterpretation resulting in undesired outcomes.

Methods: A concurrent observational evaluation of all PRN orders on a hospitalist service was conducted for a 5 day course, Monday to Friday. Information gathered included general patient characteristics, number of scheduled medications, indications for medications, and on PRN orders: dosing parameters and guidance provided was also noted. The objective of this project was to evaluate the use of PRN medications in an academic setting focusing on those that resulted in duplication of therapy.

Results: Forty-five patient medication profiles were reviewed and it was revealed that on average each patient was prescribed seven PRN medications. Notably, of the PRN medications, less than one PRN medication per patient profile provided clear parameters or additional administration instructions.

Conclusion: Anticipating a patient’s medication needs is an asset in medical care for timeliness and patient satisfaction, especially for such needs as pain management. However, when a prescribing tactic has led to undesired outcomes or harm to the patient, a re-evaluation of this practice is required.


Keywords: Medication Safety; As Needed Medications; Prescriber Communication.


The Latin term “Pro re nata,” or “PRN” as it is better known, translates to “as the situation demands” or “according to circumstance” or “as needed”[1]. The practice of writing PRN orders is common for medication prescribing in hospitals, other skilled medical facilities, and even home use. Balancing the convenience of PRN medication prescribing with patient safety is complex: defining the difference between a PRN medication and an anticipatory medication is not clear to most providers or nurses. Standing orders have demonstrated benefit in improving vaccination rates and also improving preventative screening processes [2]. Other uses for PRN medications include the anticipation of likely medical events or patient needs occurring in the absence of a physically present physician. A PRN order for a stool softener, for example, can help with patient comfort and avoid delay in care or management. Literature supports the use of anticipatory orders in the settings for palliative care and end of life comfort. In general, medical practice reliance on PRN medications has extended well beyond anticipatory


medications such as stool softeners and use of opiates in the terminally ill, to treatment of dynamic medical conditions [3]. The role of anticipatory medication in treating known, stable conditions is of clear benefit to the patient and treating practitioner alike. Less clear is the reliance on PRN medications in unknown and variable clinical scenarios, which may result in duplication of PRN medications further complicated with limited prescriber direction provided. One of the advantages PRN orders provide is flexibility in dosing based on the individual patient’s needs. A potential drawback to this type of prescribing practice is opportunity for interpretation of the requested order when guidelines for administration are limited [4].There is limited literature providing input on how to safely use this routine prescribing tactic. In a study examining the use of as needed psychiatric medications, 73% of the time PRN psychiatric medications were initiated by nurses [5]. Nurses have tremendous impact on the use of PRN medications, from administration to educating the patient of treatment options.


Following an undesired outcome involving the use of PRN medications as described in the case below, a simple medication use evaluation of PRN medication use by one service was evaluated.



A 77-year-old white female admitted to the non-teaching service from an outside nursing home following a two day history of progressive and worsening agitation, altered mental status, and suspected urinary tract infection. Past medical history included hypertension, mood disorder, Alzheimer’s Dementia, neuropathy, myelodysplastic syndrome, gastric reflux disease, depression, seizures, and chronic kidney disease stage II. During hospitalization, the patient was prescribed 13 scheduled medications and 13 PRN medications. Refer to Table 1 for a listing of the medications.


The PRN medications were prescribed within the first five hours of admission. On the first hospital day the patient’s morning blood pressure was 170/95 mmHg. At this time, the patient received scheduled amlodipine, as well as the available PRN medications: clonidine, hydralazine, and haloperidol. Both PRN blood pressure medications included parameters for use with systolic blood pressure (SBP) greater than



Scheduled Medications

PRN medications

amlodipine 5 mg PO daily

APAP* 650 mg PO Q4 PRN Temp/pain 

aspirin 81 mg PO daily 

APAP*- oxycodone 5/325 mg PO Q4 PRN pain 

enoxaparin 40 mg SQ daily

bisacodyl 10 mg PO QHS PRN constipation 

hydroxyurea 500 mg PO BID

calcium carbonate chew 500 mg TID PRN indigestion 

levofloxacin 250 mg IV daily

clonidine 0.1 mg PO Q8 PRN blood pressure 

loratadine 10 mg PO daily

dextromethorphan- guaifenesin 5 mL PO Q4 PRN cough 

multivitamin PO daily

diphenhydramine 25 mg IV Q4 PRN itch 

nicotine 14 mg patch applied transdermal daily

haloperidol 2 mg IV Q8 PRN agitation 

olanzapine 5 mg PO daily 

hydralazine 25 mg PO Q6 PRN blood pressure 

Polyethylene Glycol 17 g PO daily

magnesium hydroxide 30 mL PO PRN constipation 

risperidone 1 mg PO daily

ocular lubricant 1 app ou PRN dry eyes 

lansoprazole 30 mg PO daily

ondansetron 4 mg Q8 PRN nausea 

pregabalin 75 mg PO BID 

zolpidem 5 mg PO QHS PRN sleep




















Table 1: (BID: twice daily: 1000 and 1800; daily: 1000; QHS: 2200; TID (0800, 1300, and 1800); Q hours: every # hours permitted dosing)*APAP: acetaminophen

160 mmHg, but lacked guidance for preferred administration order or instructions for repeat blood Pressure monitoring before giving additional medications. Two hours later, noon vital signs revealed a BP of 74/38 mmHg. A subsequent BP assessed by the physician read 50/30 mmHg and the patient was noted to be unresponsive which resulted in an intensive care unit transfer. The patient was hemodynamically stabilized and transferred back to the general medicine floor two days later.


Additional safety concerns are the potential for drug interactions due to the number of concomitant medications available. For example, the number of different formulations of acetaminophen products may allow for the 24 hour administered dose to exceed a safe quantity. The multiple agents with overlapping side effect profiles creates concern for additive potential or enhanced effects leading to an altered central nervous system, sedation, and/or respiratory depression. Cardiovascular effects are also a concern due to combinations with risk of an increased potential for QT interval prolongation, exacerbation of orthostatic regulation disturbances and increased arrhythmogenic potential. This is not an all descriptive list of potential adverse effects but further insinuates the concerns with this particular case presentation.


This case illustrates the complexity of using PRN medication orders and the adverse outcomes associated with their undirected use. It also provides an opportunity for improved design of electronic order sets and careful review of systems of safety using electronic order sets. The nurse executed the physician orders as written and gave all PRN medications indicated by the orders, in this case “blood pressure.” The patient received clonidine and hydralazine in addition to scheduled amlodipine. The patient was also agitated, so the nurse gave the haloperidol at the same time as the three blood pressure medications, following her interpretation of the orders as written.


The decisions for use of PRN orders are multifaceted and include choosing between medications prescribed for the same indication, timing of administration, and route of administration. A literature search to review current practice and guidelines for PRN medication orders was conducted. Search terms used were PRN medication use, safety of PRN medications, PRN parameters, anticipatory orders, and nurse PRN. There is a paucity of published literature regarding PRN medication safety use, but an article closely related to this case evaluated the use of PRN psychiatric medication use as well as nurses’ opinions on appropriate administration of pain medications [4,5]. A study conducted by Usher and colleagues evaluated various factors influencing psychiatric PRN medication use by retrospective chart review [5]. One variable of importance, highlighted in a study done in 2001, was that the documented reason for medication administration was absent 36% of the time [5]. In 2008, the Joint Commission on Accreditation of Healthcare, or JCAHO, required an indication for all PRN medications [6]. A study conducted by Gordon and colleagues evaluating nurses’ opinions on timing of PRN pain medications and the strengths given, showed one-third to one-half of all participating nurses chose to administer a dose that did not adequately cover the patients’ need [4]. The nurses’ reasoning was based on their discomfort with the potential adverse effects associated with overdosing, but they were acting within the range provided by the limited PRN order guidance and were left to interpret what was felt to be the safest for patient care [4]. Twenty-one percent of nurses indicated that they would give less than what was ordered by the physician, in attempt to avert harmful effects to the patients [4]. The researchers of this study felt the results accurately portrayed the need for prescribers to write appropriate range orders to guide the nurses’ practice.

Due to the lack of literature and the potential impact PRN medication use can have on patient safety, we were provided with an opportunity to evaluate the PRN prescribing practices, use of parameters, and guidance within our institution.


This project was designed as an institutional review board (IRB) approved concurrent observational evaluation of the PRN prescribing practices for a non-teaching service within a large academic medical center. The non-teaching service consists of two daytime physicians along with a nurse practitioner and one physician overnight. Data was collected for all patients admitted to the service over a five day course from Monday to Friday. Inclusion criteria were patients prescribed a PRN medication. Other information collected included dosing parameters, instructions or additional direction provided, and indication. Standard demographics were collected to define the type of patients on the service, including age, race, sex, number of co-morbid diseases, and number of scheduled medications. Descriptive statistics were used for interpretation of the

Information collected. The project was approved by the IRB as part of our medication use evaluation program.


During the specified five day window of observation, 45 patients with at least one PRN medication were identified on the non-teaching service. Table 2 illustrates the types of patients on the service. On average, each patient was prescribed seven PRN medications with less than one PRN medication per patient containing parameters or additional administration directions beyond indication. Graph 1 depicts the more commonly prescribed PRN medication indications. For the patients prescribed a PRN medication, if more than one PRN order existed per indication (n=57 occurrences), 28% of those medications prescribed included parameters or additional directions for administration. For those orders that did include parameters, most were part of an alcohol withdrawal or hyperglycemic management protocol. Forty-two patients had a total of 88 PRN orders written for pain medications. Thirty-two of those patients were prescribed more than one PRN pain medication, with only two of them containing parameters for selection guidance. During two instances, the PRN medication was converted to a scheduled medication based on frequency of use data.








Table 2. Demographics with number of medication







n=45    patients


58.6     years (ave)


55%     male


55.6%  Caucasian

42.2%  African American

<3%     other

Independent disease states listed on admission

3.2 (ave; SD +/- 1.56)

Scheduled medications

8.89 (ave; SD +/- 5.67)

PRN medication

7.11 (ave; SD +/- 3.3)







PRN, standing orders, by protocol, or anticipatory orders are equivalent in their exemption of prescriber presence to implement their use. Unfortunately, parameters, boundaries for use, and guidelines are often omitted from these orders that may provide personnel with necessary details for implementation. When instruction for use is lacking, there is room for alternative interpretation, self-discretion, and clinical judgment which will vary among individuals. Parameters set by the ordering prescriber are beneficial; however guidance for their use should also be included to minimize the chance for misinterpretation and responsibility felt on behalf of personnel to determine the appropriate course of action to address the patients’ needs. An example is depicted in Table 3.






Clonidine 0.1mg po q8h PRN blood pressure

provides information for indication

For systolic blood pressure of greater than 60mmHg

parameter set

Repeat blood pressure within 30min of administration guidance

and do not give with other blood pressure medications





The data collected showed an average of seven PRN medications per patient. This was approximately two medications less than their scheduled medication load. On average, less than one PRN medication ordered provided any parameters and none provided guidance. Individuals most affected by PRN orders are nurses and patients. A lack of guided direction creates an environment where the administering nurse becomes the prescriber and manager of PRN medications. An example of this would be a patient presenting with pain and the physician prescribing ibuprofen 800mg, acetaminophen 500mg, oxycodone/acetaminophen 5/325mg, and morphine 2mg IV, with the only instructions being “PRN for pain.” When the nurse interviews the patient and the patient reports a pain score of 8, what medication would be the most appropriate to administer? The environment for lack of direction has provided the freedom and variability of clinical judgment which could result in administration of all four options at one time, or on the other end of the spectrum, could possibly under dose the pain management with a single acetaminophen tablet. At this point, the administering personnel have become the prescriber. The patient may potentially suffer with inadequately managed pain or suffer consequences from too much management. To minimize the risk of patient harm associated with the availability of multiple PRN medications, orders need to include situational instructions such as, “this medication first, may repeat in 15min” or “ only use after giving drug x first for pain score of 6-8.” This environment will present continuing challenges since it often encompasses necessary use of subjective clinical judgment, however clearer direction would be optimal and ensure that everyone is practicing as the prescriber intended.


In conclusion, this study highlights an opportunity for improving safety systems in electronic health records. The lack of automated protection in systems has the potential for patient harm. PRN medications are a convenience to physicians, and can be used successfully to anticipate patient needs and empower nurses to advance care without a phone call to the attending physician. This includes timely availability of necessary medications to the patient and limited interruptions to the prescribers for known or anticipatory medication needs. However, these conveniences can create unsafe practice environments. The observational data showed disproportional use of PRN medications lacking parameters or clinical guidance versus scheduled medications. The PRN medications most successfully used were part of a standardized protocol and provided more clear instructions to the administration personnel or nurses. Opportunities to create a safer practicing environment by providing more complete directions and also minimizing the use of PRN medications will benefit both patient and personnel.



  1. Medicine Net (2012) definitions. Definition of P.R.N. Accessed July 8, 2013.

  2. Nemeth LS, Ornstein SM, Jenkins RG, Wessell AM, Nietert PJ et al (2012) Implementing and Evaluating Electronic Standing - Orders in Primary Care Practice: A PPRNet Study. J Am Board Fam Med 25:594–604.

  3. Salins NS, Jansen W (2011) Clinical Audit on Documentation of Anticipatory “Not for Resuscitation” Orders in a Tertiary Australian Teaching Hospital. Indian J Palliat Care. 17:42-46.

  4. Gordon DB, Pellino TA, Higgins GA, Pasero C, Murphy-Ende K (2008) Nurses’ Opinions on Appropriate Administration of PRN Range Opioid Analgesic Orders for Acute Pain. Pain Management Nursing 9:131-140.

  5. Usher K, Lindsay D, Sellen J (2001) mental health nurses’ PRN psychotropic medication administration practices. Journal of Psychiatric and Mental Health Nursing 8:383-390.

  6. The Joint Commission. Diagnosis, Condition, Indication-For-Use in Order Accessed July 8, 2013.


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