IV Equivalent of 1 mg Oral Lorazepam
There is no direct IV equivalent conversion for oral lorazepam because lorazepam has nearly 100% bioavailability via both routes, making 1 mg oral approximately equal to 1 mg IV. 1
Bioavailability and Route Considerations
- Lorazepam is completely and rapidly absorbed via both oral and intramuscular routes, with IM administration reaching peak concentrations within 3 hours 1
- Following IM administration of 1.5-5 mg lorazepam, the amount delivered to the circulation is directly proportional to the dose administered, indicating consistent bioavailability 1
- A 4 mg IV dose provides an initial concentration of approximately 70 ng/mL, while a 4 mg IM dose provides a Cmax of approximately 48 ng/mL 1
- The primary difference between routes is the speed of onset, not the total bioavailability—IV administration provides immediate effect while oral/IM routes have delayed onset 1, 2
Clinical Dosing Context
- For status epilepticus, the FDA-approved IV dose is 4 mg given slowly (2 mg/min) for patients 18 years and older, which may be repeated after 10-15 minutes if seizures continue 1
- For preanesthetic sedation, the recommended IV dose is 2 mg total or 0.02 mg/lb (0.044 mg/kg), whichever is smaller, with doses up to 0.05 mg/kg (maximum 4 mg) for enhanced amnesia 1
- Patients over 50 years of age should not exceed the initial 2 mg dose for sedation 1
Important Caveats
- The rate of IV administration matters critically—lorazepam IV should not exceed 2 mg per minute to avoid respiratory depression and hypotension 1
- Lorazepam must be diluted with an equal volume of compatible solution immediately prior to IV use 1
- The clinical effect and amnesia begin more rapidly with IV administration but the total duration of action remains similar across routes 2
- Elderly patients may require dose reduction due to 20% decreased clearance, though no specific adjustment is mandated by FDA labeling based on age alone 1