Linaclotide
"I have IBS with constipation.  My GI started me on Amitiza, which worked great for 3 or 4 months, then I started having constipation again, but without the extreme cramps.  He gave me Linzess 145, which also worked great for a couple months, then not so much.  I had a colonoscopy and upper GI, which all came back normal except for an irritated stomach.  I've been on Linzess 290 now for several months, and it still works, but the way it works affects my daily plans.  It may just work too good.  I have very watery movements about 3 times every morning, and because of this I can't leave the house before noon.  I haven't had a solid stool for months.  Good thing I'm a stay at home mom!  Taking this every other day might make things better."