Sex is not a drug. Sex is (drum roll) sex. Sex is neither addictive physiologically nor is it destructive (it is creative).
As for being facetious, back at you.
BTW, here are some of the brain chemicals released when men ejaculate: dopamine, norepinephrine, serotonin, oxytocin, vasopressin, nitric oxide (NO), and the hormone prolactin. There are probably more. Those are just the ones I can think of off the top of my head.
It is these chemicals (some more than others, of course) that create the sense of euphoria in the brain.
It is of course the brain that registers pleasure (same for pain).
Just curious, why do you suppose some people engage in sex with certain people when they realize it will most likely result in STD's or even HIV?
Is it a death wish?