Both Amitiza and Linzess are used for the treatment of CIC and IBS-C. They are both prescription drugs, and both have shown similar effectiveness in relieving the problems of constipation and promoting bowel movement. Amitiza capsules are available in strengths of 8 and 24 mcg. On the other hand, the Linzess capsule is consumed once a day and is available in strengths of 72, 145, and 290 mcg, respectively.