How much lorazepam is lethal?

A surprisingly huge amount may -- or may not -- be lethal. The LD50 (lethal dose for 50% of the test exemplars) for Lorazepam is 4500mg/kg for rats, which should be pretty close to human. Therefore, a 110lb person would require about 2,250x2mg tablets just to get to the 50% lethality index. This is far more than one would likely be able to keep down.

Benzodiazepams, the family Lorazepam belongs to, is particularly not prone towards lethality.

This does NOT mean it's okay to exceed your doctor's dosage advice on this prescription only medication, as the potential for damage still exists.