What is the recommended dose of anti-anxiety medications, such as alprazolam (Xanax) or lorazepam (Ativan), prior to a Magnetic Resonance Imaging (MRI) procedure?

Recommended Dosing of Anti-Anxiety Medications Prior to MRI

For adults requiring anxiolysis before an MRI procedure, oral lorazepam 0.5-1 mg or oral midazolam 0.25-0.5 mg/kg (maximum 20 mg) administered 30-60 minutes prior to the procedure is recommended. 1

Medication Options and Dosing

First-Line Options:

Lorazepam (Ativan)

• Adult dosing: 0.5-1 mg orally 30-60 minutes before the procedure
• Onset: 15-20 minutes after oral administration
• Duration: 8-15 hours
• Advantages: No active metabolites, intermediate duration of action, less accumulation in elderly or those with hepatic impairment 1

Midazolam

• Adult dosing: 0.25-0.5 mg/kg orally (maximum 20 mg) 1
• Onset: 1-2 minutes IV, 15-30 minutes oral
• Duration: 15-80 minutes
• Advantages: Rapid onset, shorter duration, more potent than diazepam 1

Alternative Option:

Alprazolam (Xanax)

• Adult dosing: 0.25-0.5 mg orally 30-60 minutes before the procedure
• Advantages: Comparable efficacy to lorazepam with potentially fewer autonomic symptoms 2

Special Populations

Elderly Patients

• Reduce doses by at least 20% for patients over 60 years old 1
• Elderly patients are significantly more sensitive to benzodiazepine effects 1
• For lorazepam, consider 0.25-0.5 mg in elderly patients 1

Pediatric Patients

• Midazolam: 0.25-0.5 mg/kg orally (maximum 20 mg)
• Children under 6 years may require up to 1 mg/kg 1

Important Considerations

Monitoring Requirements

• Monitor respiratory status and oxygen saturation, especially when combining benzodiazepines with other sedative agents 1
• Have flumazenil available for reversal of severe respiratory depression if needed 1

Contraindications and Cautions

• Avoid or use reduced doses in patients with:
  • Severe pulmonary insufficiency
  • Severe liver disease
  • Myasthenia gravis
  • History of substance abuse 1

Common Side Effects

• Respiratory depression (especially when combined with opioids)
• Hypotension
• Paradoxical agitation (especially in children and elderly)
• Increased fall risk in elderly patients 1, 3

Clinical Approach Algorithm

1. Assess need for anxiolysis:

   • Determine severity of claustrophobia/anxiety
   • Consider patient's medical history and risk factors

2. Select appropriate medication:

   • For most adults: Lorazepam 0.5-1 mg orally
   • For procedures requiring shorter duration: Midazolam 0.25-0.5 mg/kg orally
   • For elderly: Reduce dose by at least 20%

3. Administration timing:

   • Administer 30-60 minutes before scheduled MRI
   • Ensure patient has transportation home (should not drive after receiving benzodiazepines)

4. Monitor during and after procedure:

   • Assess sedation level and vital signs
   • Monitor for respiratory depression
   • Ensure adequate recovery before discharge

Benzodiazepines should be used for the shortest possible duration to minimize risk of dependence. For MRI procedures, a single pre-procedure dose is typically sufficient and carries minimal risk of dependence or withdrawal effects 4.