What is the equivalent dose of IM Versed (midazolam) for 1 mg IV Ativan (lorazepam)?

IM Midazolam Equivalent for 1 mg IV Ativan

The equivalent dose of IM midazolam for 1 mg IV lorazepam (Ativan) is 5 mg. This conversion is based on clinical guidelines for benzodiazepine dosing in emergency and procedural settings.

Pharmacological Comparison

Potency and Onset

• Lorazepam (IV):

  • Onset: 1-5 minutes
  • Duration: 60-120 minutes
  • Standard IV dose: 0.05-0.1 mg/kg 1

• Midazolam (IM):

  • Onset: 5-15 minutes (slower than IV route)
  • Duration: 30-60 minutes
  • Standard IM dose: 0.2 mg/kg 1

Route-Specific Considerations

When converting from IV lorazepam to IM midazolam, several factors must be considered:

1. Bioavailability differences: IM midazolam has approximately 92% bioavailability 2
2. Potency ratio: Midazolam is approximately 1.5-3.5 times less potent than lorazepam on a mg-per-mg basis 1
3. Route of administration: IM administration requires higher dosing than IV for equivalent effect

Dosing Conversion Algorithm

For adult patients requiring conversion from IV lorazepam to IM midazolam:

1. Start with standard IV lorazepam dose (1 mg)
2. Apply potency conversion factor (approximately 1:5 ratio)
3. Adjust for clinical context (sedation vs. seizure management)

For seizure management specifically:

• IV lorazepam: 0.05-0.1 mg/kg (max 4 mg per dose) 1
• IM midazolam: 0.2 mg/kg (max 6 mg per dose) 1

This yields approximately a 1:5 ratio when comparing standard doses for a 70 kg adult (3.5-7 mg lorazepam IV vs. 14 mg midazolam IM).

Clinical Considerations

Patient-Specific Factors

• Age: Reduce dose by 20% or more in patients over 60 years 1
• Hepatic/renal impairment: Midazolam clearance is reduced, requiring dose adjustment 1
• Concomitant medications: Significant synergistic effects when combined with opioids 1

Monitoring Requirements

• Respiratory status (oxygen saturation)
• Level of sedation
• Vital signs
• Have flumazenil available for reversal of severe respiratory depression 1

Common Pitfalls

• Underestimation of potency differences: Midazolam is less potent than lorazepam, requiring higher doses
• Failure to account for route differences: IM administration has slower onset and may require higher initial dosing
• Oversedation risk: Particularly when combining with other CNS depressants
• Respiratory depression: More common when benzodiazepines are combined with opioids 1

Remember that the clinical context (seizure management vs. procedural sedation) may require adjustments to this general conversion ratio.