How Long Does Ativan (Lorazepam) Take to Clear from the Body?

Lorazepam has a mean half-life of approximately 12 hours in adults, with complete elimination occurring within one week after the last dose. 1, 2

Pharmacokinetic Profile of Lorazepam

Lorazepam is readily absorbed with an absolute bioavailability of 90% when taken orally 1
Peak plasma concentrations occur approximately 2 hours after oral administration 1, 3
The mean half-life of unconjugated lorazepam in human plasma is about 12 hours 1, 3
The half-life of its major metabolite, lorazepam glucuronide, is approximately 18 hours 1

Lorazepam is primarily metabolized through conjugation with glucuronic acid at its 3-hydroxy group to form lorazepam glucuronide, which is pharmacologically inactive 3, 2
70-75% of the administered dose is excreted as the glucuronide conjugate in urine 2
Approximately 88% of administered lorazepam is recovered in urine, with about 7% recovered in stool 3
The renal clearance of lorazepam glucuronide is approximately 37 ml/min 3

Age: Advancing age may affect clearance, with one study showing a 20% decrease in total body clearance in elderly subjects (60-84 years) compared to younger subjects (19-38 years) 1
Renal function: The elimination half-life of lorazepam may be increased in patients with renal failure 4
Hepatic function: Benzodiazepine clearance is reduced in patients with hepatic dysfunction 4
Population-specific differences:
- Infants: 40 hours (range 18-73 hours) 4
- Children: 10.5 hours (range 6-17 hours) 4
- Adults: 8-25 hours 5

After discontinuation of lorazepam, both the active drug and its glucuronide conjugate are completely eliminated from the blood within one week 2
Even in cases of overdose, the elimination half-life remains consistent with that observed after therapeutic doses 6

When converting from intravenous midazolam to oral lorazepam (for weaning purposes), the longer half-life of lorazepam (approximately six times longer than midazolam) must be considered 4
For patients requiring sedation assessment, the prolonged clearance time of lorazepam compared to shorter-acting benzodiazepines should be factored into clinical decision-making 4
There is no evidence of accumulation of lorazepam on administration for up to 6 months 1

When testing for the presence of lorazepam, blood samples will show detectable levels for approximately 3-5 days after the last dose in most adults 2
Urine tests may detect lorazepam metabolites for up to 1 week after the last dose 2
Complete clearance time may be extended in elderly patients or those with impaired renal or hepatic function 4, 1