LORazepam Intensol: 2 mg/mL (30 mL) [alcohol free, dye free, sugar free; unflavored flavor] Enhancement of the inhibitory effect of GABA on neuronal excitability results by increased neuronal membrane permeability to Time to Peak. Benzodiazepine, Onset of Action2, Peak Onset (hrs), Half-life parent (hrs) Clonazepam1 (Rivotril®), Int. , , -, mg. Lorazepam1 (Ativan®). Int. (po). Apr 18, - Peak concentrations of lorazepam (20 ng/mL for a 2 mg dose) in plasma For more info on the duration of lorazepam high effects, the drug's.