Linaclotide

A 14-amino-acid synthetic peptide and guanylate cyclase-C agonist, FDA-approved for irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation. It binds to guanylate cyclase-C receptors in the intestine, raising cyclic GMP levels, which increases chloride and bicarbonate secretion, slows sodium reabsorption, and draws water into the gut to soften stool and speed transit. Cyclic GMP also quiets pain-sensing nerve endings in the gut wall. The peptide is minimally absorbed into the bloodstream, acting locally in the gut.