His comments come as the Australian Sports Anti-Doping Authority continues its investigation into the use of possibly banned supplements at Essendon last season and the conduct of former Bombers employee Stephen Dank.
Demetriou wants to give greater power to club doctors, helping to prevent the potential for what he calls "a very small group" to push the boundaries.
"We are going to rid the competition of any insidious, potential lunatic sports scientists that think they're going to come in and impugn the reputation of some very, very fine people," he said on Thursday.
"There are some very, very good sports scientists out there.
"And on top of that though, there are some people out there, a very small group, that seek to damage the great nature of this game, and the great reputations of people in this game."
"There's no place for them, and the sooner they wake up to it, the better."
Demetriou said the use of illicit and performance-enhancing drugs wasn't limited to the elite level.
"It's prevalent at junior levels. We do have some 16, 17-year-olds who are trying to make it in the AFL who might think it's a good idea to perhaps look at ways that they can enhance their performance."
"That's a no-no, because inevitably you will be caught."
Demetriou said it was an issue that would be addressed through education, conceding that drug use in lower levels of the sport was high.
"I don't know how prevalent. I do know that it is. It came out in the [Australian Crime Commission] report. I think last year in the VFL competition we had a couple of cases of players testing positive. So it's there and it's real."
