What are recommended PRN (pro re nata, or as needed) medications for anxiety in elderly patients?

PRN Anxiety Medications for Elderly Patients

For elderly patients requiring PRN anxiety medication, lorazepam 0.25-0.5 mg orally is the first-line recommendation, with a maximum daily dose of 2 mg in 24 hours. 1

Primary Recommendation: Lorazepam

Lorazepam is the preferred benzodiazepine for PRN use in elderly patients due to its intermediate half-life, lack of active metabolites, and predictable pharmacokinetics. 1, 2

Dosing for Elderly Patients:

• Starting dose: 0.25-0.5 mg orally as needed 1
• Maximum: 2 mg in 24 hours (compared to 4 mg maximum in younger adults) 1
• Can be administered up to four times daily if needed 1
• Tablets can be used sublingually for faster onset (off-label use) 1
• For debilitated elderly patients, initial dosing should be 1-2 mg/day in divided doses, adjusted as tolerated 2

Alternative Options

Midazolam (If Unable to Swallow):

• 2.5-5 mg subcutaneously every 2-4 hours as required 1
• Reduce to lower doses (0.5-1 mg) in older or frail patients, especially if co-administered with antipsychotics or in patients with COPD 1
• If needed more than twice daily, consider subcutaneous infusion via syringe driver starting with 10 mg over 24 hours 1
• Reduce dose to 5 mg over 24 hours if eGFR <30 mL/min 1

Buspirone (For Chronic Anxiety, Not Acute PRN):

• Initial: 5 mg twice daily; maximum: 20 mg three times daily 1
• Useful only for mild to moderate agitation 1
• Takes 2-4 weeks to become effective, so not appropriate for true PRN use 1
• May be considered for patients requiring frequent PRN dosing who could benefit from scheduled anxiolytic therapy 3, 4, 5

Critical Safety Considerations

Why Dose Reduction is Essential in Elderly:

The NICE guidelines explicitly state to reduce benzodiazepine doses by 50-75% in elderly or debilitated patients compared to standard adult dosing. 1 This reflects:

• Increased sensitivity to benzodiazepine effects 2
• Higher risk of falls, cognitive impairment, and paradoxical agitation 1
• Potential for delirium induction 1

Important Warnings:

• Benzodiazepines themselves can cause or worsen delirium in elderly patients 1
• Increased fall risk is a major concern across all benzodiazepines in this population 1
• Avoid long half-life benzodiazepines (e.g., diazepam, flurazepam) due to cumulative toxicity 1, 6
• High-potency short-acting agents (lorazepam, alprazolam) may paradoxically cause more dependence, rebound symptoms, and memory impairment than lower-potency options like oxazepam 6
• Contraindicated in severe pulmonary insufficiency, severe liver disease, and myasthenia gravis (unless patient is imminently dying) 1

Clinical Algorithm for PRN Anxiety Management

Step 1: Address Reversible Causes First

Before prescribing any PRN medication, always explore and treat reversible causes: 1

• Explore patient's specific concerns and anxieties 1
• Ensure effective communication and orientation 1
• Treat medical causes: hypoxia, urinary retention, constipation, pain 1
• Ensure adequate lighting and environmental safety 1

Step 2: Select Appropriate PRN Medication

If patient can swallow:

• First choice: Lorazepam 0.25-0.5 mg PO PRN (max 2 mg/24h) 1
• Can use sublingually for faster onset 1

If patient cannot swallow:

• Midazolam 0.5-1 mg SC PRN (reduce from standard 2.5-5 mg dose in frail elderly) 1

Step 3: Monitor and Adjust

• Start PRN dosing initially; only convert to scheduled dosing if needed frequently (more than twice daily) 1
• Use lowest effective dose for shortest period possible 1
• Gradual taper required when discontinuing to reduce withdrawal reactions 2

What NOT to Use for PRN Anxiety in Elderly

Avoid These Medications:

• Long-acting benzodiazepines (diazepam, chlordiazepoxide, flurazepam) due to accumulation and prolonged sedation 1, 6
• Antipsychotics should generally be avoided for pure anxiety without psychosis, given black box warning for increased mortality in elderly patients with dementia 4, 7
• Beta-blockers should generally be avoided for anxiety in elderly 4
• Tricyclic antidepressants have suboptimal safety profiles for acute anxiety management 4

When to Consider Alternatives to Benzodiazepines

If patient requires frequent PRN dosing (more than twice daily), consider: 8, 4, 5

• Scheduled SSRI therapy (citalopram, escitalopram, sertraline) as first-line for chronic anxiety 4, 5
• Short-term adjunctive lorazepam during SSRI initiation (first few weeks) to bridge delayed onset of antidepressant effect 8
• Buspirone for maintenance therapy in mild-moderate generalized anxiety (not for acute PRN use) 1, 4, 5

Special Populations

Renal Impairment:

• Lorazepam preferred as it undergoes glucuronidation (not hepatic metabolism) and has no active metabolites 2, 6
• Midazolam: reduce to 5 mg/24h if eGFR <30 mL/min 1

Hepatic Impairment:

• Lorazepam or oxazepam preferred due to simpler metabolism 2, 6
• Avoid medications requiring extensive hepatic metabolism 3

Patients with COPD:

• Use lower doses (e.g., midazolam 0.5-1 mg instead of 2.5-5 mg) 1
• Exercise extreme caution due to respiratory depression risk 1