A single oral dose of Ativan (lorazepam) produces noticeable effects for roughly 6 to 8 hours, though the drug remains in your body much longer than that. The average half-life is about 12 hours, meaning it takes around 2.5 days for a dose to be nearly fully eliminated. The half-life of Ativan, the amount of time it takes an individual’s system to metabolize the drug to half its original concentration in the bloodstream, is often stated to be about 12 hours; however, a better estimate is between 10 and 20 hours for most individuals. While it is a fast-acting drug, Ativan has a relatively long half-life. A medication's half-life refers to the amount of time its concentration in the body reduces by half which, in the case of Ativan, is every 12 hours. 2 The half-life of Ativan (lorazepam) is 10 to 20 hours, with an average of about 12 hours in healthy adults. That means it takes roughly 12 hours for your body to eliminate half of a single dose from your bloodstream. It takes about five half-lives (roughly 60 hours or 2.5 days) for Ativan to be nearly eliminated from your system. The half-life differs from duration of effects, as you may feel calmer for 6 to 8 hours while the drug remains in your body longer. Ativan is metabolized by the liver and eliminated mostly by the kidneys. Its half-life is around 12 hours, which means that half of the drug has been eliminated within this time. It usually takes five half-lives to eliminate the greater majority (almost 97%) of a substance from your body. “Half-life” is a measure of how long it takes until half of the drug becomes inactivated. Since several of the benzos are metabolized into other benzos, to understand the full impact of a benzo, you must include its active (benzo-like) metabolites, as this table does. Lorazepam and its metabolite cross the human placenta. Teratogenic effects in humans have been observed with some benzodiazepines (including lorazepam); however, additional studies are needed. Half-Life of Ativan (Lorazepam) The elimination half-life of lorazepam is approximately 12 hours in adults, with a range of 8-25 hours depending on individual patient factors. 1 This ativan half life calculator shows how ativan accumulates and how long it stays in your body. Get dose and frequency with ease!.