Lorazepam pharmacokinetics and molecular data

Pharmacokinetics
Absorption Activity Plasma levels Effect of age on pharmacokinetics

Absorption
Lorazepam is readily absorbed with an absolute bioavailability of 90 percent. Peak concentrations in plasma occur approximately 2 hours following administration. The peak plasma level of Lorazepam from a 2 mg dose is approximately 20 ng/mL. Return to top

Activity
The mean half-life of unconjugated Lorazepam in human plasma is about 12 hours and for its major metabolite, Lorazepam glucuronide, about 18 hours. At clinically relevant concentrations, Lorazepam is approximately 85% bound to plasma proteins. Lorazepam is rapidly conjugated at its 3-hydroxy group into Lorazepam glucuronide which is then excreted in the urine. Lorazepam glucuronide has no demonstrable CNS activity in animals. Return to top

Plasma levels
The plasma levels of Lorazepam are proportional to the dose given. There is no evidence of accumulation of Lorazepam on administration up to six months. Return to top

Effect of age on pharmacokinetics
Studies comparing young and elderly subjects have shown that advancing age does not have a significant effect on the pharmacokinetics of Lorazepam. However, in one study involving single intravenous doses of 1.5 to 3 mg of Lorazepam injection, mean total body clearance of Lorazepam decreased by 20% in 15 elderly subjects of 60 to 84 years of age compared to that in 15 younger subjects of 19 to 38 years of age. Return to top