lol wut.
i think most H1 blockers are considered complimentary to opiates. i wouldnt say potentiators, because that implies some biochemical interaction. i think they tend to cut down on histamine release and add a somnolent effect.
there is something going on with H1 antagonists and dopamine though. some people seem to love benadryl and demerol IV together. and i remember reading something about H1 and the expectation of reward in the mesolimbic pathway (reward center).