Iboga. The Bark from a west African tree was researched by the C.I.A. during their MK-ULTRA trials in the 1950's.It not only eased the pain of opium withdraws by 95% (Not a weasel statistic) but it reset the human brain to a pre dependent state of awareness.
Because, however, it was a psycho-tropic substance- the compound (Ibogaine Hydrochloride) was declared a class 1 narcotic and banned from human consumption by federal officials.