My Wife, Aged 46, Is A Patient Of Multiple Sclerosis,

My wife, aged 46, is a patient of Multiple Sclerosis, which was diagnosed when she was about 30. Her condition is stable, apart from that she has difficulty in walking. Her main problem now is constipation. She does not pass stool for several days and I have used a plethora of medicines. Constipation is taking toll now on her health as she has very small appetite. Kindly suggest a remedy.