Pharmacodynamic effects of Sandostatin in the gastrointestinal tract.

Somatostatin is widely distributed throughout the human gastrointestinal system. There it is found in neurons and fibers of both the submucosal and the myenteric plexus and the pancreas as well as in the D cells of the stomach, gut and pancreatic islets. Whereas in the intestinal nervous system, in the duodenum and the pancreas, somatostatin-14 appears to be the predominant molecular form, the endocrine-type D cells of the intestine primarily contain somatostatin-28. Somatostatin peptides may act very differently at different sites, as hormones, as paracrine substances or neurotransmitters. Because of this complexity of action, very little is known about the physiological effects of somatostatin in the gastrointestinal tract. In contrast, the pharmacological actions of natural synthetic somatostatin have been thoroughly studied and have given rise to many therapeutic applications. Octreotide, an analogue with a longer half-life and higher potency, has greatly facilitated the clinical application of somatostatin. This review deals with the pharmacological effects of octreotide on different gastrointestinal functions. The somatostatin analogue exerts a long-lasting inhibitory action on gastric acid, pancreatic enzyme and bicarbonate secretion as well as on bile flow. It is also able to inhibit stimulated intestinal secretion, the release of neuropeptides from the gut and the pancreas. It can also prolong orocecum transit time and prevent gallbladder contraction. It inhibits absorption of nutrients and exerts inhibitory effects on splanchnic hemodynamics. It is because of these actions that somatostatin has attracted so much attention in the treatment of different gastrointestinal disorders.