Gonna agree here. I'm Rh Neg and muscle relaxers cause intense pain for me. Morphine has never blunted pain for me, other narcotics just give me tics. Codeine is all that works, but I need more of it than normal. A shots of Novocaine gives me a strange pleasant thrill through my whole body. Valium and Xanax have zero effect on me. Marijuana makes me hallucinate. Most medications have paradoxical effects. I never equated any of it to my blood group status.