What is a suitable PRN (pro re nata, or as needed) medication for a 78-year-old patient?

PRN Medication Recommendations for a 78-Year-Old Patient

For a 78-year-old patient, acetaminophen is the most appropriate PRN medication due to its demonstrated effectiveness and good safety profile compared to alternatives like NSAIDs which carry significant risks in elderly patients.

First-Line PRN Options

Acetaminophen

• Recommended as initial and ongoing PRN pharmacotherapy for pain, particularly musculoskeletal pain, due to its demonstrated effectiveness and good safety profile in older adults 1
• Dosing recommendations for elderly patients:
  • Maximum daily dose should not exceed 4g per 24 hours, including "hidden sources" from combination medications 1
  • Standard adult dosing: 2 caplets (650mg) every 8 hours with water, not exceeding 6 caplets in 24 hours 2
  • Should be swallowed whole; not crushed, chewed, split or dissolved 2
• Contraindications:
  • Absolute: liver failure 1
  • Relative: hepatic insufficiency, chronic alcohol abuse or dependence 1

Second-Line PRN Options (Use with Extreme Caution)

NSAIDs (including Ketorolac)

• Should be considered rarely and with extreme caution in highly selected elderly individuals 1
• Absolute contraindications in elderly patients:
  • Active or history of peptic ulcer disease 3
  • Age >60 years (already a risk factor) 3
  • Chronic kidney disease 3
  • Heart failure 3
  • Thrombocytopenia or concurrent use of anticoagulants 3
• If NSAIDs must be used:
  • Treatment should not exceed 5 days 3
  • Use the smallest effective dose 1
  • Patients should use a proton pump inhibitor or misoprostol for gastrointestinal protection 1
  • Regular monitoring of blood pressure, renal function, and electrolytes is required 1, 3

PRN Medications for Specific Symptoms

For Nausea/Vomiting

• Ondansetron 8mg IV q8h or prochlorperazine 10mg IV q6h PRN 1
• Lorazepam 0.5mg IV q6h PRN can be considered as an alternative 1

For Diarrhea

• Loperamide 2mg every 2 hours PRN after ruling out gastrointestinal infection 1
• Diphenoxylate/atropine two tablets PO q6h PRN for diarrhea refractory to loperamide 1

For Pruritus/Itching

• Diphenhydramine 25mg PO q6h PRN or hydroxyzine 10mg PO q6h PRN 1
• Caution: antihistamines can cause confusion in elderly patients 4

Important Considerations for PRN Medications in the Elderly

Polypharmacy Concerns

• Elderly patients are at increased risk for adverse drug reactions due to polypharmacy, age-related physiological changes, and multiple disease states 1, 5
• Before prescribing any PRN medication, evaluate glomerular filtration rate as renal function is usually markedly depressed in very old individuals 5

Documentation and Administration

• Ensure proper documentation of PRN medication administration 6
• Provide clear patient education about when and how to take PRN medications 6

Monitoring Requirements

• Regular assessment for adverse effects is essential when prescribing PRN medications to elderly patients 1
• For patients taking NSAIDs: monitor for gastrointestinal and renal toxicity, hypertension, heart failure, and drug-drug interactions 1

Avoiding Common Pitfalls

• Avoid prescribing multiple medications with similar side effect profiles (e.g., multiple medications that can cause sedation) 1
• Be aware of the "prescribing cascade" where a drug is prescribed to treat side effects of another medication 7
• Limit drug prescription to essential medications and periodically re-evaluate all medication use in elderly patients 5
• Consider non-pharmacological interventions for pain management when appropriate 1