What is the equivalent dose of clonazepam for a patient taking Ativan (lorazepam) 0.5mg twice a day (BID)?

Clonazepam Equivalent Dose for Lorazepam 0.5mg BID

For a patient taking lorazepam 0.5mg twice daily (total 1mg/day), the equivalent clonazepam dose is 0.5mg daily, which can be given as a single dose or divided into 0.25mg twice daily.

Conversion Ratio

The standard benzodiazepine equivalency ratio between lorazepam and clonazepam is approximately 2:1, meaning lorazepam 1mg is equivalent to clonazepam 0.5mg 1. This conversion is based on comparative sedative potency studies demonstrating that diazepam 10mg equals lorazepam 2-2.5mg, and clonazepam has similar potency to diazepam on a milligram basis 1.

Dosing Strategy

• Start with clonazepam 0.5mg daily (equivalent to the total daily lorazepam dose of 1mg) 2
• Dosing frequency options:
  • Single daily dose of 0.5mg (preferred due to clonazepam's long half-life of 30-40 hours) 2
  • Divided dose of 0.25mg twice daily if the patient prefers more frequent dosing or experiences breakthrough symptoms 2

Critical Pharmacokinetic Differences

Clonazepam has a significantly longer half-life (30-40 hours) compared to lorazepam, which fundamentally changes the dosing approach 2. This means:

• Clonazepam provides more sustained coverage throughout the day with less frequent dosing 2
• Peak plasma concentrations occur within 1-4 hours with 90% bioavailability 2
• The longer duration of action reduces the need for BID dosing that was necessary with lorazepam 2

Monitoring and Adjustment

• Monitor closely for clinical response after conversion, as individual patient factors may require dose adjustment 2
• Watch for increased sedation initially, as clonazepam's longer half-life means accumulation over the first few days 2
• Common side effects include sedation, impaired coordination, confusion, and memory dysfunction 2

Special Population Considerations

• Elderly or hepatically impaired patients: Consider starting with clonazepam 0.25mg daily (lower than the calculated equivalent) and titrate up as needed 2
• Women may require different dosing than men to achieve equivalent symptom control 2
• Renal impairment: Dose adjustment may be necessary 2

Important Caveats

• Avoid combining clonazepam with other CNS depressants without careful monitoring 2
• Use with extreme caution in patients with neurodegenerative disorders, obstructive sleep apnea, or underlying liver disease 2
• The combination of benzodiazepines with certain antipsychotics (particularly clozapine) should be avoided or used with great caution due to risk of delirium 3