I actually found it on youtube and started watching the part I had missed before I was interrupted. Couldn't find it again later. The heroin/opiate one and the cocaine/ecstacy are still available there.
I just googled and found it via Torrent, so I guess I'll try dl'ing it.
(History Channel) - Hooked - Illegal Drugs & How They Got That Way - Marihuana | Bitenova