Lorazepam to Diazepam (Valium) Dose Equivalency
Lorazepam 1 mg is equivalent to diazepam 5 mg, making lorazepam approximately 5 times more potent than diazepam. 1
Standard Conversion Ratio
- The conversion ratio is 1:5 (lorazepam:diazepam), meaning 1 mg of lorazepam equals approximately 5 mg of diazepam 1
- This conversion applies across different routes of administration and clinical contexts 2
Clinical Pharmacology Differences
While the drugs are dose-equivalent, they differ significantly in their clinical behavior:
Onset and Duration
- Diazepam has a faster onset (2-5 minutes IV) compared to lorazepam (15-20 minutes IV) 2
- Lorazepam has a longer duration of clinical effect despite diazepam's much longer elimination half-life (8-15 hours for lorazepam vs 20-120 hours for diazepam) 2, 3
- This paradox occurs because diazepam is highly lipid-soluble and rapidly redistributes from the brain to peripheral tissues, terminating its clinical effect within 2 hours, while lorazepam's effects can last up to 72 hours 3, 4
Metabolism and Active Metabolites
- Diazepam produces active metabolites that prolong sedation, especially in renal failure patients 2
- Lorazepam has no active metabolites, making it more predictable in patients with renal dysfunction 2
Practical Conversion Examples
When converting between these medications:
- Lorazepam 2 mg = Diazepam 10 mg 1
- Lorazepam 0.5 mg = Diazepam 2.5 mg 1
- For ICU sedation: lorazepam loading dose 0.02-0.04 mg/kg equals diazepam loading dose 5-10 mg 2
Important Clinical Caveats
- Both drugs cause respiratory depression and hypotension, especially when combined with opioids 2
- Diazepam causes phlebitis when injected into peripheral veins, while lorazepam has lower risk of venous thrombosis 2, 1
- In elderly patients, reduce doses by 50% for both medications due to increased sensitivity 2, 5
- Lorazepam's elimination half-life increases in renal failure, requiring dose adjustment 2
- Diazepam's active metabolites accumulate with prolonged use, particularly problematic in renal dysfunction 2