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 Ativan (Lorazepam) is 12 hours for unconjugated lorazepam and 18 hours for its major metabolite, lorazepam glucuronide 1.
- The half-life of the active form of the drug, unconjugated lorazepam, is the primary consideration for clinical use.
- Key points to consider are the pharmacokinetics and metabolism of the drug.
From the Research
Half-Life of Ativan (Lorazepam)
The half-life of Ativan (Lorazepam) is reported to vary across different studies.
- Typical kinetic values for lorazepam are: elimination half-life, 8 to 25 hours 2
- Values of elimination half-life (t1/2beta) in the elderly (15.9 hr) did not differ significantly from those in the young group (14.1 hr) 3
- Variable half-lives were found (range 9.3-32.1 h, mean about 20 h) 4
- The apparent elimination half-life of lorazepam was about 12 hr 5
- Lorazepam can be classified as an intermediate-acting benzodiazepine, with a half-life value between 5-24 hours 6
Factors Influencing Half-Life
Several factors can influence the half-life of lorazepam, including:
- Age: lorazepam clearance is somewhat reduced in old age 2, but age differences in lorazepam clearance were partly explained by more frequent cigarette smoking in the young subjects 3
- Liver disease: liver disease has a minimal effect on lorazepam clearance 2, but may impair clearance in long-acting benzodiazepines 6
- Renal disease: renal disease is associated with a prolonged half-life and increased volume of distribution of oxazepam, but its effect on lorazepam is not well-studied 2