In this prospective, randomized, double blind study, the aim is to determine the efficacy of Linaclotide in relation to Senna in relieving the symptoms of chronic idiopathic constipation (CIC). Patients with CIC, (age 18 - 70) will be enrolled in the study and randomized to Senna or Linaclotide. Patients will be asked to complete questionnaires during the study and will be followed for 12 weeks. Main outcomes include number of daily bowel movements and measures from surveys regarding bowel habits, relief, and satisfaction.