Linaclotide is an agonist of guanylate cyclase-C (GC-C). Once linaclotide and its active metabolite binds to GC-C, it has local effect on the luminal surface of the intestinal epithelium. Activation of GC-C by linaclotide results in the intra- and extracellular increase of cyclic guanosine monophosphate concentrations (cGMP). This elevation of cGMP levels stimulates the secretion of chloride and bicarbonate into the intestinal lumen via activation of cystic fibrosis transmembrane conductance regulator (CFTR) ion channel. Ultimately, linaclotide helps patients with IBS (especially with constipation) as GI transit is accelerated and the release of intestinal fluid is increased. In animal models, a decrease in visceral pain after administration of linaclotide may be observed. A decrease in the activity of pain-sensing nerves occurs as a result of an increase in extracellular cGMP.
Changes in the appearance and consistency of stools as measured by the Bristol Stool Form Scale (BSFS) have been noted after taking linaclotide.
Linaclotide is metabolized within the gastrointestinal tract to its principal, active metabolite, MM-419447, by loss of the terminal tyrosine moiety. Both linaclotide and the metabolite are proteolytically degraded within the intestinal lumen to smaller peptides and naturally occurring amino acids.
Most common adverse reactions (incidence of at least 2%) reported in IBS-C or CIC patients are diarrhea, abdominal pain, flatulence and abdominal distension.
Busby RW, Kessler MM, Bartolini WP, Bryant AP, Hannig G, Higgins CS, Solinga RM, Tobin JV, Wakefield JD, Kurtz CB, Currie MG: Pharmacologic properties, metabolism, and disposition of linaclotide, a novel therapeutic peptide approved for the treatment of irritable bowel syndrome with constipation and chronic idiopathic constipation. J Pharmacol Exp Ther. 2013 Jan;344(1):196-206. doi: 10.1124/jpet.112.199430. Epub 2012 Oct 22. Pubmed