General:
https://www.bestmedicaldegrees.com/10-dangerous-drugs-once-marketed-as-medicine/
https://www.bustle.com/articles/72089-5-illegal-drugs-that-were-once-used-in-everyday-products-from-meth-diet-pills-to-heroin
https://www.therichest.com/rich-list/most-shocking/10-illegal-drugs-you-wont-believe-used-to-be-legal/
https://dondivamag.com/10-illegal-drugs-that-used-to-be-sold-over-the-counter/
https://www.attn.com/stories/1934/why-is-opium-illegal
Nembutal:
http://abcnews.go.com/Health/MindMoodNews/story?id=5481482
https://en.wikipedia.org/wiki/Pentobarbital

Quaaludes:
http://www.bbc.com/news/magazine-33428487
G.H.B.:
https://www.vice.com/en_us/article/qbxexv/dark-side-of-ghb-narcomania-003
https://en.wikipedia.org/wiki/Gamma-Hydroxybutyric_acid

Amy Nitrites:
https://www.vice.com/en_us/article/wdpa5y/hey-straight-people-youre-using-sex-drugs-wrong

Methamphetamine:
http://www.drugfreeworld.org/drugfacts/crystalmeth/history-of-methamphetamine.html
Morphine:
https://science.howstuffworks.com/life/biology-fields/10-bizarre-treatments8.htm
https://en.wikipedia.org/wiki/Morphine