Octreotide, a new somatostatin analogue.

The chemistry, pharmacology, pharmacokinetics, clinical uses, adverse effects and drug interactions, dosage, availability and cost, and indications for use of octreotide, a new synthetic analogue of the peptide hormone somatostatin (SS), are reviewed. Like SS, octreotide suppresses secretion of pituitary growth hormone (GH) and thyrotropin and decreases release of a variety of pancreatic islet cell hormones including insulin, glucagon, and vasoactive intestinal peptide (VIP). Octreotide also reduces splanchnic blood flow, gastric acid secretion, GI motility, and pancreatic exocrine function and alters the absorption of water, electrolytes, and nutrients from the GI tract. The elimination half-life of i.v. octreotide is 72-98 minutes, compared with 2-3 minutes for i.v. SS. Usual administration of octreotide is by the i.v. or s.c. route. Octreotide has been studied in the treatment of hormone-secreting pituitary tumors and pancreatic islet cell tumors. Octreotide therapy lowers GH secretion and improves clinical symptoms in patients with acromegaly and may suppress clinical symptoms to a greater degree than bromocriptine. Patients with carcinoid syndrome and VIP-secreting tumors (vipomas) have had substantial improvement in clinical symptoms with administration of octreotide. This agent does not appear to be effective in the treatment of nonvariceal upper GI bleeding and acute pancreatitis; its relative usefulness in the treatment of variceal bleeding is not established. Adverse effects associated with octreotide therapy generally have been mild, including pain or burning at the injection site, abdominal pain, and diarrhea. Octreotide has been shown to interfere with absorption of oral cyclosporine. Standard initial therapy is octreotide acetate 50-100 micrograms s.c. every 8-12 hours, with titration based on clinical and biochemical effects. Up to 3000 micrograms/day of octreotide acetate has been administered to patients with acromegaly without serious adverse effect. Octreotide is marketed under the brand name Sandostatin and is available in 1-mL ampuls containing 50, 100, and 500 micrograms of octreotide acetate. Because the conditions for which octreotide appears to be most effective are uncommon, the drug should be considered for addition to the formulary in tertiary-care institutions only; addition of octreotide to the formulary of a community hospital is probably unnecessary. The synthetic analogue octreotide is longer acting and more specific in pharmacologic action than SS.(ABSTRACT TRUNCATED AT 400 WORDS)