Benzodiazepine Equivalence: Diazepam and Lorazepam
For benzodiazepine equivalence, 10 mg of diazepam (Valium) is approximately equivalent to 2-2.5 mg of lorazepam (Ativan), with important clinical differences in their pharmacokinetics and applications.
Potency and Equivalence
- Lorazepam is approximately 4-5 times more potent than diazepam 1
- Standard equivalence:
- 10 mg diazepam = 2-2.5 mg lorazepam 1
Key Pharmacokinetic Differences
Absorption
- Diazepam: Better absorbed orally than intramuscularly
- Lorazepam: Similar absorption via both oral and intramuscular routes 1
Onset and Duration
- Diazepam: More rapid onset but shorter duration
- Lorazepam: Slower onset but significantly longer duration of action 1, 2
Distribution and Metabolism
Diazepam:
- Longer elimination half-life (average 51.2 hours)
- Higher lipid solubility
- Larger volume of distribution (133 L/kg for unbound drug)
- Has active metabolites
Lorazepam:
- Shorter elimination half-life (average 15.7 hours)
- Lower lipid solubility
- Smaller volume of distribution (12 L/kg for unbound drug)
- No active metabolites 2
Clinical Applications and Preferences
Status Epilepticus
- If IV access is available, both lorazepam and diazepam are effective
- Lorazepam is preferred over diazepam for status epilepticus due to:
Hepatic Dysfunction
- Lorazepam is preferred in patients with:
- Hepatic dysfunction
- Advanced age
- Serious medical comorbidities
- This is due to its metabolism primarily through glucuronide conjugation rather than hepatic pathways 6
Safety Considerations
Respiratory Depression
- Both medications can cause respiratory depression, especially when combined with other CNS depressants
- Lorazepam shows lower rates of respiratory depression (4.4%) compared to diazepam (5.6%) in status epilepticus treatment 4
Venous Complications
- Lorazepam IV administration is associated with fewer venous thrombosis complications compared to diazepam 1
Dependence and Withdrawal
- Both medications carry risks of:
Important Cautions
- Never abruptly discontinue either medication after prolonged use; implement a gradual taper over 2-12 weeks
- Avoid concurrent use with opioids, alcohol, or other CNS depressants due to increased risk of severe respiratory depression and death
- Elderly patients have heightened sensitivity to all benzodiazepine effects and require lower dosing
- Monitor for paradoxical reactions including increased anxiety, agitation, and irritability 6, 7
By understanding these equivalence relationships and clinical differences between diazepam and lorazepam, clinicians can make more informed decisions when selecting the appropriate benzodiazepine for specific clinical scenarios.