So I have this friendwho enjoys a painkiller or two when he hangs out at bars/relaxes instead of drinking alcohol, because he needed to quit. Does this affect his muscle growth at all, kind of an akward question but I was wondering if any research has been done on this. If he needs to he'll quit it for the sake of growth. But I've heard from doctors that I've asked that Hydrocodone in and of itself isn't harmful to the body, the tylenol that accompanies most mixtures is hard on the liver though. any input?