I know a guy who has always taken 10x more substances than anyone else, and seems to still crave more. I watched him eat an entire handful of Percocet once, and then work all day like it was nothing. Half of one of the pills he took knocked me on my ass. I puked, then passed out, and slept for six hours. He was eating like 8 of them at a time, several times per day. He does the same thing with alcohol, and any other drugs he can get his hands on.