Inclusion criteria:  Meet Rome IV criteria for IBS-C Patients given informed written consent  Exclusion Criteria:  Current treatment with laxative or SSRI Use of any medication indicated for treatment of IBS within preceding 2 weeks of enrollment Organic disorder of the large or small bowel (e.g. inflammatory bowel disease, tuberculosis, diverticular disease) Diagnosis of any medical condition associated with constipation except IBS-C (e.g DM, Hypothyroidism, CVD, parkinsonism) Clinical feature suggestive of organic disease (e.g. unexplained significant weight loss, rectal bleeding) Previous gastrointestinal or abdominal surgery (except for common causes unrelated to IBS) Abnormal laboratory tests (CBC, CRP, RBS, S. Creatinine, S.TSH, ECG) Mechanical obstruction Known severe depression, psychiatric disorder. Pregnancy or lactation