|Systematic (IUPAC) name|
|Pregnancy cat.||B (US)|
|Legal status||℞ Prescription only|
|Routes||Subcutaneous, intramuscular, intravenous|
|Bioavailability||100%; I.M.: 60% to 63% of subcutaneous dose|
|Mol. mass||1019.24 g/mol|
| (what is this?)
Octreotide (brand name Sandostatin, Novartis Pharmaceuticals) is an octapeptide that mimics natural somatostatin pharmacologically, though it is a more potent inhibitor of growth hormone, glucagon, and insulin than the natural hormone. It was first synthesized in 1979 by the chemist Wilfried Bauer.
Approved uses 
The Food and Drug Administration (FDA) has approved the usage of a salt form of this peptide, octreotide acetate, as an injectable depot formulation for the treatment of acromegaly, gigantism, thyrotropinoma, diarrhea and flushing episodes associated with carcinoid syndrome, and diarrhea in patients with vasoactive intestinal peptide-secreting tumors (VIPomas).
Octreotide is used in nuclear medicine imaging by labelling with indium-111 (Octreoscan) to noninvasively image neuroendocrine and other tumours expressing somatostatin receptors. More recently, it has been radiolabelled with gallium-68, enabling imaging with positron emission tomography (PET), which provides higher resolution and sensitivity.
Octreotide can also be labelled with a variety of radionuclides, such as yttrium-90 or lutetium-177, to enable peptide receptor radionuclide therapy (PRRT) for the treatment of unresectable neuroendocrine tumours.
Off-label and experimental uses 
Octreotide has also been used off-label for the treatment of severe, refractory diarrhea from other causes. It is used in toxicology for the treatment of prolonged recurrent hypoglycemia after sulfonylurea and possibly meglitinides overdose. It has also been used with varying degrees of success in infants with nesidioblastosis to help decrease insulin hypersecretion.
The drug has been used off-label, injected subcutaneously, in the management of hypertrophic pulmonary osteoarthropathy (HPOA) secondary to non-small cell lung carcinoma. Although its mechanism is not known, it appears to reduce the pain associated with HPOA.
It has been used in the treatment of malignant bowel obstruction.
Octreotide may be used in conjunction with midodrine to partially reverse peripheral vasodilation in the hepatorenal syndrome. By increasing systemic vascular resistance, these drugs reduce shunting and improve renal perfusion, prolonging survival until definitive treatment with liver transplant. Similarly, octreotide can be used to treat refractory chronic hypotension.
Octreotide has not been adequately studied for the treatment of children, pregnant and lactating women. The drug is given to these groups of patients only if a risk-benefit analysis is positive.
Adverse effects 
The most frequent adverse effects (more than 10% of patients) are headache, hypothyroidism, cardiac conduction changes, gastrointestinal reactions (including cramps, nausea/vomiting and diarrhoea or constipation), gallstones, reduction of insulin release, hyperglycemia or hypoglycemia, and (usually transient) injection site reactions. Slow heart rate, skin reactions such as pruritus, hyperbilirubinemia, hypothyroidism, dizziness and dyspnoea are also fairly common (more than 1%). Rare side effects include acute anaphylactic reactions, pancreatitis and hepatitis. One study reported a possible association with rheumatoid arthritis.
Octreotide is absorbed quickly and completely after subcutaneous application. Maximal plasma concentration is reached after 30 minutes. The elimination half-life is 100 minutes (1.7 hours) on average when applied subcutaneously; after intravenous injection, the substance is eliminated in two phases with half-lives of 10 and 90 minutes, respectively.
Pharmacological effects 
Since octreotide resembles somatostatin in physiological activities, it can:
- inhibit secretion of many hormones, such as gastrin, cholecystokinin, glucagon, growth hormone, insulin, secretin, pancreatic polypeptide, TSH, and vasoactive intestinal peptide,
- reduce secretion of fluids by the intestine and pancreas,
- reduce gastrointestinal motility and inhibit contraction of the gallbladder,
- inhibit the action of certain hormones from the anterior pituitary,
- cause vasoconstriction in the blood vessels, and
- reduce portal vessel pressures in bleeding varices.
Octreotide can reduce the intestinal resorption of ciclosporin, possibly making it necessary to increase the dose. Patients with diabetes mellitus might need less insulin or oral antidiabetics when treated with octreotide. The bioavailability of bromocriptine is increased; besides being an antiparkinsonian, bromocriptine is also used for the treatment of acromegaly.
See also 
- Octreotate, a closely related peptide
- Medscape: Octreoscan review
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