I originally sent this post as a PM to SwampFox to avoid cluttering the other thread, but seeing as this is its own thread now..
I don't think including endogenous substances as "drugs" is a very useful definition. Normally when people think of "drugs" small molecule chemicals like morphine, pseudoephedrine, THC, etc. etc. come to mind. But there are also drugs that are enzymatic proteins (Butyrylcholinesterase), or small peptides (HGH).
So now if you use your definition, all neurotransmitters, all enzymes, and every small peptide produced by your body falls under the category "drug." There are also RNA/DNA based drugs, so with your definition you'd also have to include all genetic material in your body as a "drug" as well.
Here's the full FDA definition of a drug (probably the most universally accepted definition): "according to the Food, Drug, and Cosmetic Act (1) : a substance recognized in an official pharmacopoeia or formulary (2) : a substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease (3) : a substance other than food intended to affect the structure or function of the body (4) : a substance intended for use as a component of a medicine but not a device or a component, part, or accessory of a device"
Intent is a big part of the definition. I don't see any way endogenous substances could fall under this definition of drug. It might seem strange that dopamine in your brain doesn't count as a drug, but extracting, concentrating and consuming that same dopamine "to affect the structure or function of your body" makes it a drug, but that's what the word means.
edit:
say I painstakingly extract testosterone from my piss, it's still a "drug" if I administer it later.
Sounds like a good idea, what solvent do you recommend?
