Lorazepam to Diazepam Conversion
0.25 mg of lorazepam (Ativan) is equivalent to approximately 2.5 mg of diazepam. 1
Conversion Rationale
The conversion between lorazepam and diazepam follows a potency ratio of approximately 1:10, meaning lorazepam is about 10 times more potent than diazepam on a milligram-per-milligram basis. This conversion is supported by clinical evidence:
- British Journal of Anaesthesia research established that 2-2.5 mg of lorazepam is equivalent to 10 mg of diazepam 1
- Therefore, 0.25 mg of lorazepam would be equivalent to 2.5 mg of diazepam
Key Pharmacological Differences
When converting between these benzodiazepines, it's important to consider their distinct pharmacological properties:
Duration of Action
- Lorazepam: Intermediate-acting with effects lasting 6-8 hours
- Diazepam: Longer-acting with effects lasting 24-48 hours due to active metabolites
Onset of Action
- Lorazepam: Slower onset (30-60 minutes oral)
- Diazepam: Faster onset (15-30 minutes oral) 1
Metabolism
- Lorazepam: Primarily conjugated in the liver without active metabolites
- Diazepam: Metabolized by the liver with several active metabolites (including desmethyldiazepam)
Clinical Considerations
When converting between these medications:
Withdrawal Risk: Diazepam's longer half-life provides a natural tapering effect, potentially reducing withdrawal symptoms
Sedation Profile: Diazepam may cause more initial sedation but lorazepam's effects may be more sustained 2
Special Populations:
- Elderly: Consider starting with lower doses of either medication due to increased sensitivity
- Hepatic Impairment: Lorazepam may be preferred due to its simpler metabolism
Route of Administration:
- Diazepam has variable intramuscular absorption
- Lorazepam has more consistent absorption across different routes 1
Practical Application
When transitioning from lorazepam to diazepam:
- Convert 0.25 mg lorazepam to 2.5 mg diazepam
- Consider dividing the diazepam dose if sedation is a concern
- Monitor for breakthrough symptoms or excessive sedation
- Be aware that the clinical effects of diazepam may begin more rapidly but the effects of lorazepam typically last longer 1
Remember that while this conversion ratio is generally accepted, individual patient factors including age, comorbidities, concomitant medications, and the indication for therapy should be considered when making this conversion.