Without wanting to burst anyone's bubble, I'm guessing that the words actually refer to a dose of serious palliative care grade painkillers.

I don't like the emphasis on "last words" anyway. When I'm dying (and probably not especially lucid), I don't want to have to cope with the pressure that any set of words could be my last and hence I'd better make 'em good. I think we should let everyone record their official last words ahead of time, just so there's one less thing to worry about when you're actually dying.