Linaclotide (marketed under the trade name Linzess and Constella) is a peptide agonist of the guanylate cyclase 2C (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. The metabolite of linaclotide MM-419447 (CCEYCCNPACTGC) contributes to the pharmacologic effects of linaclotide. 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. It was approved by the FDA in August 2012 for the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation (IBS-C) in adults.

Indium In-111 pentetate disodium is a radioactive diagnostic indicated for use in radionuclide cisternography. Decay of In-111 by electron capture allows for detection with a gamma camera for visualization of the brain and spinal column. Indium In 111 pentetate ( 111In-DTPA) is indicated as an imaging agent in cisternography to study the flow of cerebrospinal fluid (CSF) in the brain, to diagnose abnormalities in CSF circulation, to assess and help localize the site of CSF leakage, and to test the patency of or localize blocks in CSF shunts.