Peak effects roughly coincide with peak serum levels, which occur 10 minutes after intravenous injection, up to 60 minutes after intramuscular injection, and 90 to 120 minutes after oral administration, but initial effects will be noted before this.

Lorazepam is considered to be a short-acting drug which, similar to other benzodiazepines, exerts its therapeutic as well as adverse effects via its interaction at benzodiazepine binding sites, which are located on GABAA receptors in the central nervous system. If shown sympathy, even quite crudely feigned, patients may respond solicitously, but they may respond with disproportionate aggression to frustrating cues. Therefore, lorazepam's anticonvulsant effects are more durable, thus reducing the need for repeated doses. This medication can increase the effects of alcohol. Synergistic adverse effects may also occur when lorazepam is administered with other drugs such as opioids or other hypnotics. The resulting benzodiazepin-4-oxide undergoes acetylation by acetic anhydride at the secondary nitrogen atom, and is further hydrolyzed by hydrochloric acid into 7-chloro-5-(2′-chlorophenyl)-1,2- dihydro-3H-1,4-benzodiazepin-2-on-4-oxide. See also: Ativan pregnancy and breastfeeding warnings (in more detail)The sedative effects of this medication may last longer in older adults. S. This is because the brain has spare benzodiazepine drug receptor capacity, with single, clinical doses leading only to an occupancy of some 3% of the available receptors. The likelihood of dependence is relatively high with lorazepam compared to other benzodiazepines.