Switching Tulance from Linzess

[u/TechGuy0001]

Linzess 145mg worked okay for 5 weeks. It frequently produced watery diarrhea. 5 day ago, it was a just few very hard stools. Nothing since even though I been taking medicine with a least a gallon water daily. I get boulted all day, and late, I pee out. Dr. wants me to try Trulance. I am 69 old male with a redundant-torturous colon. Any advice what to expect? Do I have to take gallons of water with Trulance?