Can Tizanidine And Morphone Together Cause Dizziness, Tachycardia, Swelling And Fingers Tingling?

My wife takes a muscle relaxer (Tizanadrine) and a pain killer (Morphine ER 60 MG) and has been having night episodes of dizziness, weakness, rapid heart beat, feeling of need to vomit, swelling, and tingling of fingers. I believe this is interactions of the 2 drugs. Is this the case in your opinion? What do you recommend?