Benzodiazepine Dose Conversion: Lorazepam to Clonazepam
For a patient taking 1 mg of lorazepam, the equivalent dose of clonazepam is 0.5 mg, based on the standard 2:1 conversion ratio. 1
Standard Conversion Ratio
- Clonazepam is approximately twice as potent as lorazepam, meaning 1 mg of clonazepam equals 2 mg of lorazepam 1
- Therefore, 1 mg lorazepam converts to 0.5 mg clonazepam 1
- This 2:1 ratio is supported by the American Academy of Pediatrics and applies most reliably to anxiolysis, sedation, and acute agitation management 1
Critical Pharmacokinetic Differences to Consider
When making this conversion, recognize these important distinctions:
- Clonazepam has a dramatically longer half-life (30-40 hours) compared to lorazepam, which affects dosing frequency and accumulation risk 2, 3
- Lorazepam has faster onset of action (peak effect at 3-5 minutes IV), while clonazepam reaches maximum plasma concentrations in 1-4 hours 1, 3
- Clonazepam has 90% bioavailability after oral administration 2, 3
- The metabolic pathways differ: lorazepam undergoes direct conjugation and elimination, while clonazepam follows different hepatic metabolism 1
Practical Conversion Strategy
Start with the equivalent dose (0.5 mg clonazepam for 1 mg lorazepam) and monitor closely for clinical response. 3 However, adjust based on these factors:
- For elderly patients or those with hepatic impairment, consider starting lower than the calculated equivalent dose 3
- Women may require higher doses than men to achieve the same clinical effect 2, 3
- Patients with renal impairment may need dose adjustments 3
Monitoring for Side Effects After Conversion
Watch for these common adverse effects with clonazepam:
- Morning sedation (most common) 2
- Early morning motor incoordination 2
- Confusion and memory dysfunction 2
- Risk of falls, particularly at higher doses 2
- Potential worsening of sleep apnea 2
Use clonazepam with particular caution in patients with neurodegenerative disorders, obstructive sleep apnea, or underlying liver disease. 2, 3
Respiratory Depression Risk
Both medications can cause respiratory depression, especially when combined with opioids or other CNS depressants, requiring monitoring of oxygen saturation and preparation to provide respiratory support if needed 2, 1
Common Pitfall to Avoid
Do not assume equivalent dosing frequency when converting. Because clonazepam's half-life is 30-40 hours compared to lorazepam's shorter duration, clonazepam typically requires less frequent dosing (often once or twice daily versus lorazepam's typical three to four times daily). 3