I'm with the "nothing"'s on this one; if my lover is passed out under the influence, how is she going to appreciate all of my mad bedroom skills?
And as for pleasuring myself, I only really get off if she gets off, so it's not much of a turn-on for me...
Truth be told, as my SO never uses and almost never drinks, if I had to come home to the above-described scenario, I'd probably grab a big stick and start looking for traces of the bastard who slipped my lady a roofie colada!
This is all coming from the perspective of a long-term, tender-loving relationship, though - I might think very differently if this came from a person with whom I was only involved for sex... I love my girl too much to just "make use" of her, even if she asks...