I've had serious GI issues before and during opiate use. I was recently in the hospital for a bowel impaction and it is no fun. Don't EVER let it get to the point where you have a blockage. By that point it doesn't matter the laxatives you take (in fact they make it worse) because you have feces that has formed a huge blockage. I couldn't pee because the blockage was pressing on something and my kidney was inflamed. I had taken miralax and used glycerin tabs to try and go that day. The doctor and the nurse told me I would need a manual desimpaction (? spelling). However the laxatives made that impossible because they made everything soft which blocked the blockage. So if you are already impacted stool softeners can make it more complicated. I ended up getting an enema. They say it makes you go right away.... not in my case. I had to sit on the toilet and wait. It was painful but the blockage eventually came out. Now I am very conscious about this and I would rather go through a little withdrawal one day then ever have the doctor try and desimpact me again. Unfortunately for me withdrawal doesn't alleviate my constipation and if you have a blockage it won't either.
So DRINK DRINK DRINK. Water, tea, coffee. But lots of water is good. If you can't stand it then juice but water is so important. Yogurt with raisins. Lots of yummy frozen yogurt. All sorts of vegetables and fruits. Don't eat many pizzas, breads, sandwiches, potato, pasta, etc. Exercise. Crunches. When I am on an opiate run I tend to not eat which actually makes constipation worse. Miralax is helpful when I'm not already very constipated. Otherwise it just causes pain because it is moving things that don't want to come out. After so much opiate use my muscles that push are very weak.