IV Lorazepam to IV Diazepam Conversion
The conversion ratio from IV lorazepam to IV diazepam is approximately 1:2 to 1:2.5, meaning 1 mg of IV lorazepam is equivalent to 2-2.5 mg of IV diazepam. 1
Conversion Ratio and Potency Differences
- Lorazepam is approximately twice as potent as diazepam, with 2-2.5 mg of lorazepam providing equivalent sedative effects to 10 mg of diazepam 1
- When converting from IV lorazepam to IV diazepam, multiply the lorazepam dose by 2 to 2.5 to determine the equivalent diazepam dose 1
- For example, if a patient is receiving 4 mg IV lorazepam, the equivalent IV diazepam dose would be 8-10 mg 1
Critical Pharmacokinetic Differences to Consider
Duration of action differs significantly between these agents, which impacts clinical decision-making beyond simple dose conversion:
- Diazepam has a much shorter duration of anticonvulsant activity (<2 hours) compared to lorazepam (up to 72 hours) 2
- Diazepam is rapidly redistributed from the brain, with seizures often recurring within 15-20 minutes, necessitating immediate administration of a long-acting anticonvulsant like phenytoin or fosphenytoin 3, 4
- Lorazepam provides prolonged anticonvulsant coverage and may be preferred for status epilepticus management due to its longer duration of action 3, 2
Clinical Efficacy Considerations
Lorazepam demonstrates superior efficacy in seizure management compared to diazepam:
- In out-of-hospital status epilepticus, lorazepam terminated seizures in 59.1% of patients versus 42.6% for diazepam (odds ratio 1.9,95% CI 0.8-4.4) 5
- Both agents show similar safety profiles regarding respiratory depression (10.6% for lorazepam vs 10.3% for diazepam) 5
- Lorazepam as monotherapy is as effective as the diazepam-phenytoin combination in pediatric convulsive status epilepticus, with 100% success rates in both groups 6
Important Caveats When Converting
- The conversion ratio applies to sedative equivalence, but clinical context matters: if converting for seizure management, lorazepam's longer duration of action means you may need more frequent diazepam dosing or concurrent long-acting anticonvulsant coverage 3, 2
- Respiratory monitoring is essential with both agents, particularly when combined with other CNS depressants 3, 4
- Venous thrombosis occurs less frequently with IV lorazepam compared to IV diazepam 1
- The IM route is not recommended for diazepam due to tissue necrosis risk, whereas lorazepam can be given IM 3
Practical Dosing Algorithm
When converting from IV lorazepam to IV diazepam:
- Calculate the equivalent dose: Multiply lorazepam dose by 2-2.5 1
- Administer diazepam slowly over approximately 2 minutes to avoid pain at the IV site 3
- For seizure management, immediately follow with a long-acting anticonvulsant (phenytoin 18 mg/kg IV or fosphenytoin 20 mg PE/kg) due to diazepam's short duration 3, 4
- Monitor for respiratory depression and have ventilatory support immediately available 3, 4
- Consider whether conversion is clinically appropriate: lorazepam may be the superior choice for ongoing seizure management given its longer duration of action 2, 5