OxyContin and feelings

My husband has been taking Oxycontin for about four years after many other meds that didn't take care of the pain. He has had two failed back surgeries and really needs this for the pain. Some times I think that it's a good medication and other times not. The withdrawls are the most awful thing I have ever seen in my life. He can not sleep, he kicks his feet, rolls around on the bed just trying to get away from the feelings. He says it feels like his legs are on fire. It made me cry to see him like that and I hope I never see that again.
Charlotte