Hello Xanax is a benzodiazepine which has many side effects like any medication, including muscle cramps, muscle rigidity and muscle tone disorder. Your wife has a fibromyalgia which affects muscle tones and there s an evidence of muscle weakness caused by dialysis by losing proteins during the process. The muscle weakness might be caused by a contribution of previous situations which needs a medical review by her doctor. I suggest that you consult her doctor to make the right assessment of her condition. Hope I answered your question Wish your wife a speedy recovery Best regards Dr. Noor Farid