PRN Medications
Indications & Use
Bindu Swaroop, MD
Fundamentals of Medicine
July 2014
Objectives
• Identify which prn medications are appropriate for inclusion in
admission orders
• Identify contraindications and adverse effects associated with
common prn medications
• Known when to evaluate the patient prior to ordering or the
nurse giving a prn medication
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Common Uses
• Sleep
• Pain
• Cardiovascular: Hypertension
• Sedatives: ETOH withdrawal, agitation
• Pulmonary: Nebulizers, Mucolytics
• GI: Bowels, Heartburn
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Case Vignette
HPI: 59 year old male admitted for chest pain and acute
ETOH intoxication. He also complains of hematemesis
during his most recent drinking binge.
PMHx: AVNRT, Hepatitis C, insomnia, depression, COPD
Meds: combivent inhaler bid, ibuprofen 600mg po tid
prn
EKG on admission reveals AVNRT @111 bpm
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Case Vignette
He is admitted to the medicine service with the following prn
orders:
-Ativan 2mg IV q4hr prn withdrawal
-Albuterol neb q6h prn, Atrovent neb q6hr prn
-Acetaminophen 650mg q4hr prn pain
-Ibuprofen 600mg po tid prn pain
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Case Vignette
That night the patient subsequently requests pain medication for his chest
pain. It is determined by the night float that there is no evidence of ACS.
Since ibuprofen is ordered prn the night float instructs the nurse to give
this to the patient. The patient still complains of pain later that night, and
the night float writes an order for Morphine sulfate 2mg IVP q4hr prn pain.
Are these appropriate meds to give to the patient?
What other alternatives could have been given?
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Analgesics
NonOpiods
Opiods
Oral
Pain Severity
SC/IM/IV
Pain Severity Adverse Effects
Acetaminophen
325-650mg
Mild
Ketorolac
30-60mg
Moderate
Ibuprofen
600-800mg
Mild
Tramadol
50-100mg
Mild to
Moderate
Tylenol w/
codeine
Mild to
Moderate
Morphine
Moderate to
Severe
Constipation, Ileus,
n/v, respiratory
depression, urinary
retention
Moderate
Dilaudid
Severe
Caution Hepatic or
Renal Impairment
Moderate
Fentanyl (IV or
patch)
Severe
PUD, GI bleed,
renal toxicity
30mg-60mg/300mg
Vicodin
(5mg/300mg)
Norco
(10mg/325mg)
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Percocet
(5mg/325mg)
Caution in hepatic
or renal
impairment
Case Vignette
The next day his BP has risen to 170/105. He is given hydralazine
10mg IVP by the team with a drop in his BP to 125/78.
3. What is likely contributing to the rise in BP?
4. What side effects could occur from lowering the BP too much?
5. How else could this patient have been treated?
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Hypertension
Goal:
-To identify and treat the underlying cause
-Prevent end-organ damage
Common Causes:
Rebound
Inadequate dosing
Drug Interactions
ETOH withdrawal
Hypoxemia, respiratory distress
Pain, Anxiety
Autonomic response: urinary retention, constipation, SCI
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Hypertension
Approach to evaluating the patient:
-Determine patient’s baseline
-Confirm accuracy, both arms, cuff size
-Screen for the underlying cause
-Determine if hypertensive emergency or urgency is
present
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Hypertension Treatment
Hypertensive Urgency
-SBP >180 or DBP >120
-gradual reduction of BP to 160/110 over 24-48 hours
-use ORAL meds
Hypertensive Emergency
-evidence of end-organ damage
-Immediate reduction of SBP by 15-20%
-Use PARENTERAL agents and transfer to ICU
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Hypertension Clinical Pearls
• Hypertensive treatment rarely requires immediate treatment in
the middle of the night
• Avoid prn use of rapid acting agents (can precipitate ischemic
events)
• For patients with sustained HTN, primary team should initiate
treatment with long acting regimen
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Case Vignette
Later that night the patient requests something for sleep and
receives Benadryl 25mg po, written as qhs prn per night float. On
day three of admission he develops urinary retention with a PVR
of 300cc. A foley catheter is placed. You review his chart and
notice a prior urology note indicating the patients prostate size on
DRE is 50g.
What could be contributing to the urinary retention?
What other alternatives could have been used for his insomnia?
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Hypnotics
Benadryl
25mg-50mg
Beers high severity
Anti-cholinergic effects
(confusion, dry mouth, urinary
retention, wheezing; caution in
pts with glaucoma and BPH
Temazepam (Restoril)
15-30mg
(geriatric 7.5mg)
Beers high severity
Same AE as any benzo;
contraindicated in glaucoma
caution in those with falls risk,
hepatic or renal impairment
Trazodone (unlabeled use)
25-50mg
Okay in elderly
Hypotension, increased bleeding
risk if on NSAID’s or warfarin,
priapism, serotonin syndrome,
caution post-MI or with h/o
seizures
Zolpidem (Ambien)
5-10mg
Okay in elderly
HA, dizziness, caution in those
with respiratory compromise,
myasthenia gravis
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Case Vignette
He remains hospitalized due to social issues including
homelessness. On day 4 of admission you are called by
the nurse due to the patient falling in his room. You
evaluate his gait and notice he is unsteady in addition to
being more somnolent than usual.
What could be contributing to the fall and gait
impairment?
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Sedatives
Ativan: common use in ETOH withdrawal
-AE include sedation, respiratory depression
-Caution in those with acute angle glaucoma, sleep apnea,
respiratory issues, hepatic/renal impairment, h/o drug
abuse or falls risk
Anti-Psychotics: Typical (Haldol) & Atypical (Seroquel, Risperidone)
-anti-cholinergic side effects, QT prolongation
-careful in dementia related psychosis (increased risk of
death compared to placebo)
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Case Vignette
A review indicates the patient has continued to receive
Ativan despite no further evidence of withdrawal due to
complaints of anxiety and insomnia.
A review of his chart reveals he was previously on mirtazapine
but this medication had not been continued on admission.
During rounds, it is noted that the tachycardia noted on
admission is persistent.
What else could be contributing to the tachycardia?
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Pulmonary
•Nebulizers:
– Albuterol (max dose 3mL q4hours): can cause tachycardia, arrhythmia,
caution in patients with ischemia
– Atrovent: anti-cholinergic side effects; caution in those with glaucoma,
BPH
•Mucolytics:
– Mucomyst: can cause bronchospasm; use 10-20 minutes after
bronchodilator administration
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Case Vignette
The patient subsequently complains of diarrhea the next day.
Stool studies are sent, and the intern orders lomotil prn for loose
stools.
Is this an appropriate order?
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Gastrointestinal
Heartburn: Maalox (aluminum dioxide, magnesium hydroxide) or
Maalox plus
AE: constipation, cramps, fecal discoloration; aluminum intoxication
– Use with caution in renal impairment: hypophosphatemia or
hypermagnesemia
– long list of drug interactions
– Must be administered one hour apart from other oral meds
Constipation: phosphate (fleets) enema
– Do not use in patients with renal impairment, ascites, heart failure,
GI obstruction or megacolon
Diarrhea: do not use in those with c.difficile colitis
– Loperamide (Immodium): caution in hepatic impairment
– Lomotil (diphenoxylate/atropine): anti-cholinergic side effects)
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Case Vignette
The patient subsequently does well and is discharged. Upon
discharging the patient, you order the following outpatient
medication regimen:
• Ibuprofen 600mg po tid prn
• Vicodin 2 tabs q6hr prn
• Combivent inhaler q4hr prn
• Benadryl 25mg po qhs prn
• Librium taper
Are these appropriate orders?
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Summary
•For all PRN orders, know the correct dosage, common adverse
effects and contraindications
•Check the next day to see if your patient actually received any of
the PRN meds
•Convert frequently administered PRN meds into standing orders
•Don’t just put in PRN orders to save night float the “trouble” of
getting called
•Evaluate underlying cause or condition requiring use of a PRN
med and treat accordingly
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