Trulance for Constipation. Any thoughts

Has anyone tried Trulance for chronic constipation? I had trouble before my colonoscopy prep but nothing seems to be working, not miralax or magnesium citrate. My colon has just stopped moving and my GI recommends Trulance. I've tried fiber and low wheat and lots of water.

Any thoughts?

Yes, he wrote me a prescription which the insurance company denied. I'm waiting on a preauthorization. Expensive.

The colonoscopy prep always shuts down my system from working, but the problem was happening before just not as bad. Even 2 bottles of magnesium citrate didn't clean me out.