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). Our hypothesis is that Senna is not inferior to Linaclotide in the treatment of CIC. Seventy patients aged 18-70 diagnosed with CIC and seen by a gastroenterologist affiliated with TriHealth or a patient of the Faculty Medical Center clinic will be included in the study. After enrollment, subjects will be randomized to receive either Linaclotide or Senna over a 12-week period after a 1 week wash-out period. During th study period, subjects will complete a log to record the number of daily bowel movements. The subjects will also complete 3 validated surveys on a weekly basis: Subject's Global Assessment SGA of Relief, Subject's Global Assessment SGA of Bowel Habit, and SGA of Satisfaction with their Bowel Habit. A research nurse will meet with subjects at the beginning of the study and then at 3 monthly visits to administer the study medication and distribute the surveys. The main outcomes measures are change in # of bowel movements and SGA survey scores.