What is the half-life of Lorazepam (Ativan)?

From the Guidelines

The half-life of lorazepam is approximately 40.2 hours in infants and 10.5 hours in children. This information is based on a study published in the journal Pediatrics in 2011 1. The half-life of lorazepam can vary depending on the age of the patient, with infants having a significantly longer half-life compared to children. Key points to consider include:

• The half-life of lorazepam in infants is approximately 40 hours, with a range of 18-73 hours.
• The half-life of lorazepam in children is approximately 10.5 hours, with a range of 6-17 hours.
• The metabolism of lorazepam may be affected by organ dysfunction and hypothermia, which can impact the drug's half-life and therapeutic levels.
• It is essential to consider the total amount of administered medication and its potential impact on drug metabolism and levels when determining the appropriate time interval for testing after discontinuation 1. In clinical practice, the half-life of lorazepam is crucial in determining the timing of neurologic examinations to determine brain death, and physicians should be aware of the potential for accumulation of the drug with repeated dosing.

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. Following parenteral administration, the terminal half-life and total clearance averaged 14±5 hours and 1.1±0. 4 mL/min/kg, respectively.

The half-life of Lorazepam is approximately 12 hours for the oral form and 14 hours for the parenteral form. 2 3

From the Research

Lorazepam Half-Life

• The half-life of Lorazepam is approximately 12 hours, as indicated by a study published in 1978 4.
• Another study from 1977 reported an elimination half-life of 13.6 hours for unchanged Lorazepam 5.
• A study published in 2012 found that the half-life of Lorazepam in pediatric patients was around 16.8 hours 6.
• A comparison of oral and sublingual Lorazepam formulations in 1983 reported average elimination half-lives of 8 hours for oral and 11 hours for sublingual doses 7.

Factors Affecting Half-Life

• The half-life of Lorazepam may be influenced by factors such as age, dosage, and formulation, as suggested by the varying half-lives reported in different studies 4, 5, 6, 7.
• However, a review of benzodiazepines published in 2021 does not provide specific information on the half-life of Lorazepam 8.

Pharmacokinetics

• Lorazepam is rapidly absorbed and reaches peak concentrations in the blood within 2-3 hours after oral administration 4.
• The drug is primarily metabolized through conjugation with glucuronic acid to form inactive lorazepam glucuronide, which is then excreted in the urine 4, 5.