What are suitable PRN (pro re nata) medications for anxiety and agitation in a 78-year-old patient?

PRN Medications for Anxiety and Agitation in a 78-Year-Old Patient

For elderly patients with anxiety and agitation, low-dose benzodiazepines and antipsychotics are the most appropriate PRN medications, with lorazepam 0.25-0.5mg being the first-line option for anxiety and haloperidol 0.5mg for delirium-related agitation. 1

First-Line Options

For Anxiety (Patient Able to Swallow)

• Lorazepam 0.25-0.5mg orally four times a day as required (maximum 2mg in 24 hours for elderly patients) 1
• Oral tablets can be used sublingually (off-label use) for faster onset 1
• Lorazepam is preferred over other benzodiazepines due to its intermediate half-life and absence of active metabolites 2

For Anxiety (Patient Unable to Swallow)

• Midazolam 2.5mg subcutaneously every 2-4 hours as required 1
• Reduce dose to 5mg over 24 hours if estimated glomerular filtration rate (eGFR) is <30 mL/minute 1

For Delirium with Agitation (Patient Able to Swallow)

• Haloperidol 0.5mg orally at night and every 2 hours when required 1
• Maximum daily dose should be limited to 5mg in elderly patients 1
• Low-dose haloperidol (≤0.5mg) has been shown to be as effective as higher doses with fewer side effects 3

Second-Line Options

Atypical Antipsychotics

• Quetiapine 25mg (immediate release) orally as needed 1
  • Less likely to cause extrapyramidal side effects than other antipsychotics
  • May cause orthostatic hypotension and dizziness
• Olanzapine 2.5mg orally as needed 1, 4
  • Reduce dose in older patients
  • Available as orally disintegrating tablet
  • WARNING: Increased mortality in elderly patients with dementia-related psychosis 4
• Risperidone 0.5mg orally as needed 1
  • Reduce dose in patients with severe renal or hepatic impairment

Important Considerations

Before Starting Medication

• Address reversible causes of anxiety, delirium, and agitation first 1:
  • Explore patient's concerns and anxieties
  • Ensure effective communication and orientation
  • Ensure adequate lighting
  • Treat physical causes like hypoxia, urinary retention, or constipation

Cautions with Benzodiazepines

• Increased risk of falls 1
• Use lower doses in frail elderly patients or those with COPD 1
• May cause paradoxical agitation, especially in elderly 1
• May worsen delirium in some cases 5

Cautions with Antipsychotics

• Haloperidol and other antipsychotics can themselves cause increased agitation and delirium 1
• Higher doses of haloperidol (>1mg) significantly increase risk of sedation without improving efficacy 5, 3
• Antipsychotics should be used for the shortest period possible 1

Monitoring

• Monitor for orthostatic hypotension, especially with quetiapine and olanzapine 1
• Watch for extrapyramidal side effects with all antipsychotics, especially at higher doses 1
• Assess response to PRN medications to determine if scheduled dosing might be needed for persistent symptoms 1

Algorithm for PRN Selection

1. For anxiety without delirium: Start with lorazepam 0.25-0.5mg orally PRN 1
2. For delirium with agitation: Start with haloperidol 0.5mg orally PRN 1, 3
3. If first-line treatment is ineffective or contraindicated, consider second-line options like quetiapine or olanzapine 1
4. For severe agitation unresponsive to single agents, consider adding a benzodiazepine to an antipsychotic, but monitor closely for oversedation 1