From the FDA Drug Label
The mean half-life of unconjugated lorazepam in human plasma is about 12 hours and for its major metabolite, lorazepam glucuronide, about 18 hours. The half-life of lorazepam in adults is 12 hours for unconjugated lorazepam and 18 hours for its major metabolite, lorazepam glucuronide 1.
- The half-life is the time it takes for the concentration of the drug to reduce by half in the plasma.
- This information is based on studies in healthy volunteers.
- Key points:
- Half-life of unconjugated lorazepam: 12 hours
- Half-life of lorazepam glucuronide: 18 hours
From the Research
The half-life of lorazepam (Ativan) in adults is approximately 12 hours, with a typical range of 10-20 hours, as reported in the most recent and highest quality study available 2. This means it takes about 12 hours for the concentration of lorazepam in the bloodstream to decrease by half. Lorazepam has an intermediate duration of action compared to other benzodiazepines, making it suitable for both acute anxiety management and short-term treatment of insomnia. The drug is metabolized primarily in the liver through glucuronidation, which is less affected by aging or liver disease than oxidative metabolism pathways used by many other benzodiazepines. Some key points to consider include:
- The elimination half-life of lorazepam can vary, with a range of 8 to 25 hours reported in some studies 3.
- The half-life can be prolonged in elderly patients, those with renal impairment, or severe liver disease, potentially leading to drug accumulation with repeated dosing 4.
- Despite its 12-hour half-life, the clinical effects of lorazepam may last 6-8 hours for most therapeutic uses.
- Lorazepam is rapidly and extensively absorbed after oral administration, with peak plasma concentrations reached within 2 hours 5. However, the most recent study 2 provides the most accurate estimate of the half-life, which is essential for guiding clinical practice and ensuring optimal patient outcomes in terms of morbidity, mortality, and quality of life.