Benzodiazepine Equivalency: Diazepam to Lorazepam
Lorazepam is approximately 5 times more potent than diazepam, meaning 1 mg of lorazepam is equivalent to 5 mg of diazepam (or conversely, 10 mg diazepam equals 2-2.5 mg lorazepam). 1
Standard Conversion Ratio
- 10 mg diazepam = 2-2.5 mg lorazepam 1
- This represents a potency ratio of approximately 5:1 (diazepam:lorazepam) 1
- For practical clinical use: divide the diazepam dose by 5 to obtain the equivalent lorazepam dose 1
Key Pharmacokinetic Differences
While the doses are equivalent in terms of sedative potency, these medications differ significantly in their clinical profiles:
Time Course of Action
- Diazepam: Clinical effect and amnesia begin more rapidly (peaks in 2-3 minutes IV), but duration is shorter (<2 hours for anticonvulsant effect) 1, 2
- Lorazepam: Has a latent period of 8-15 minutes with increasing effects at 15-30 minutes, but provides longer duration of action (up to 72 hours) 1, 2, 3
Route-Specific Considerations
- Diazepam: Better absorbed orally than intramuscularly; should not be given IM 1
- Lorazepam: Equally well absorbed via oral or IM routes 1
- IV administration: Lorazepam causes less venous thrombosis compared to diazepam 1
Clinical Context Applications
For Acute Seizures/Status Epilepticus
- Despite equivalent initial efficacy, lorazepam's longer duration of action (up to 72 hours) makes it preferable for sustained seizure control compared to diazepam's brief effect 2
- Lorazepam efficacy: 82-100% (IV route) 2
- Diazepam efficacy: 54-100% (IV route), 28.6-100% (rectal route) 2
For Anxiety/Sedation
- Lorazepam 0.5-1 mg orally four times daily (maximum 4 mg/24 hours) is standard dosing 4
- Reduce to 0.25-0.5 mg in elderly or debilitated patients (maximum 2 mg/24 hours) 4
- For acute agitation: Lorazepam 1 mg SC/IV (up to 2 mg maximum) 4
For Benzodiazepine Withdrawal/Weaning
- When converting from continuous IV midazolam to oral lorazepam: lorazepam is twice as potent as midazolam with a sixfold longer half-life, so divide the 24-hour midazolam dose by 12 to determine daily lorazepam dose 4
Important Clinical Caveats
- Elderly patients: Use lower doses (0.25-0.5 mg lorazepam vs standard 0.5-1 mg) due to increased sensitivity and risk of falls 4
- Renal impairment: Lorazepam may have advantages in patients with hepatic dysfunction as it undergoes glucuronidation rather than oxidative metabolism 5
- Paradoxical agitation: Occurs in approximately 10% of patients treated with benzodiazepines 4
- Tolerance and dependence: Regular use leads to tolerance, addiction, depression, and cognitive impairment; use lowest effective doses infrequently 4
- Respiratory depression: Increased risk when combined with other sedatives; be prepared to provide respiratory support 4