If using Ativan (lorazepam) for anxiety during an MRI, how soon before the scan should it be taken?

Timing of Lorazepam Administration for MRI Anxiety

Take lorazepam 1.5-2 hours before your scheduled MRI scan time to ensure peak anxiolytic effect when you enter the scanner. 1

Optimal Timing Window

• Lorazepam requires 1.5-2 hours after oral administration to reach peak plasma levels and maximum therapeutic effect. 1, 2
• Effective concentrations are obtained within 30-60 minutes, but peak anxiolytic activity occurs at 1.5-2 hours. 2
• Taking the medication too close to scan time (e.g., 30 minutes before) will result in subtherapeutic levels during the procedure. 1

Recommended Dosing

• Standard adult dose: 0.5-1 mg orally, with a maximum single dose of 2 mg for procedural anxiety. 1
• For patients with moderate to severe anxiety, 2 mg represents a safe and appropriate dose for non-elderly, non-debilitated adults. 3
• Elderly or debilitated patients should receive reduced doses of 0.25-0.5 mg (maximum 0.5 mg per dose) due to increased risk of excessive sedation. 1, 4

Critical Safety Instructions

• Do not consume any alcohol when taking lorazepam, as this combination significantly increases sedation, cognitive impairment, and risk of respiratory depression. 1
• Arrange transportation home after the MRI, as lorazepam causes sedation that persists for several hours. 2
• Effects last 4-6 hours, with residual CNS effects potentially present for up to 24 hours. 2

Monitoring Considerations

• Approximately 10% of patients experience paradoxical agitation with benzodiazepines rather than sedation. 1, 5
• If you have respiratory disease (COPD, asthma), inform your physician, as lower doses may be needed due to respiratory depression risk. 1
• Patients should be monitored for up to 2 hours post-procedure for excessive sedation or respiratory effects. 5

Common Pitfalls to Avoid

• Do not take lorazepam immediately before leaving for the MRI (e.g., 15-30 minutes prior)—this timing is too short for adequate absorption. 1
• Avoid taking the medication too early (e.g., 3-4 hours before), as peak effect will have passed by scan time. 1, 2
• Do not use subtherapeutic doses repeatedly, as this increases anticipatory anxiety without clinical benefit. 3