What does this have to do with drugs?
Hold your fucking horses, I'm getting to that
So, alchemists had this deep interest in trying to find out a way with these theories to form gold from base metals, including theorizing a possible material called the philosopher's stone that could do that exact thing. They also thought the philosopher's stone could possibly grant immortality as well. Their theories were interesting, though of course flawed in some capaticies as they didn't have the full understanding of the natural world that we have today. They thought to interact with the natural world you had to interact through religion, which didn't leave much room for thought outside of that.
It did, however, lay the basis for modern chemistry.
A lot of their theory, however flawed, did make some interesting breakthroughs into science. These slowly morphed as our understanding of things grew. Eventually we knew the true building blocks for the world, as well as how to manipulate them to make new creations out of them. From cannabis to spice, from ergot to LSD. We knew how to isolate and change the makeup of chemicals. At some point though, we lost a spark that alchemy had.
Alchemy while flawed in many regards did hold some more truth to it than was thought before. The goal of a narcoalchemist is to take what was lost from alchemy and put it back into chemistry, in the goal of achieving chemical perfection in our works. We refine and distill chemicals into a more magical counterpart, something more pure and more potent, something that can influence our world in ways previously thought impossible. And, yes, we are also after the philosopher's stone.