Octreotide

Somatostatin analogue: OCTREOTIDE

SOMATOSTATIN is a key regulatory peptide of lower GI function - overall, it:
- decreases intestinal fluid secretion
- has dose dependent effects on GI motility:
  - low doses stimulate motility
  - high doses inhibit motility
- has a short half-life (3 minutes) that limits its use as a pharmaceutical agent

OCTREOTIDE is a synthetic analogue of SOMATOSTATIN, with a t½ of 1.5 hours by IV, 6-12 hours when given SC (can also be given monthly by IM injection)

inhibition of the effects of carcinoid tumors and VIPomas (you will hear more about these in the Endocrine course)
off-label use for severe diarrhea due to vagotomy or dumping syndrome, short bowel syndrome, AIDS
- you may ask why vagotomy is listed here as producing severe diarrhea, since in other circumstances, vagotomy decreases motility and produces constipation
- to quote Schwarz’s Principles of Medicine (available via Access Medicine):
  “Diarrhea following gastric surgery may be the result of truncal vagotomy, dumping, or malabsorption. Truncal vagotomy is associated with clinically significant diarrhea in 5 to 10% of patients. … The cause of postvagotomy diarrhea is unclear. Possible mechanisms include intestinal dysmotility and accelerated transit, bile acid malabsorption, rapid gastric emptying, and bacterial overgrowth.”

impaired pancreatic secretion à malabsorption of fats à fat-soluble vitamin deficiency and steatorrhea
impaired GI motility à nausea, abdominal pain, flatulence
inhibition of gallbladder contractility à gallstones (50% of patients), acute cholecystitis (rare)
altered balance among insulin, glucagon and growth hormone à hyper- or hypo-glycemia
hypothyroidism, bradycardia