Up-and-down procedure

Up-and-down procedure (or method) is an alternative to the LD₅₀ test, in which animals are used for acute toxicity testing.[1][2] It requires fewer animals to achieve similar accuracy as the LD₅₀ test because animals are dosed one at a time.[3] If the first animal survives, the dose for the next animal is increased; if it dies, the dose is decreased. It is usual to observe each animal for 1 or 2 days before dosing the next animal, however, surviving animals should be monitored for 7 days in case of delayed death. The up-and-down method is not recommended where deaths beyond 2 days are the norm.[4] The U.S. Food and Drug Administration has begun to approve non-animal alternatives.[5][6]