Nearly two weeks ago I did something horrible to my back; the doctor has me on diazepam, volterol and zydol. I had a very curious reaction where my upper torso went numb and itched really badly; I also spent quite a lot of time in an alternative reality. The doc decided it was the (anti)histamine(?) in the zydol and I've stopped taking it; sure enough all those effects have stopped. However, the diazepam and the volterol are not enough to keep the pain at bay, and I am seriously tempted to take zydol anyway. How damaging are those side-effects likely to be if I take the occasional one?