Octreotide

Octreotide

---

Octreotide is indicated for the treatment of acromegaly, symptom relief associated with gastro-entero-pancreatic tumours (eg carcinoid tumours, VIPomas), and to reduce complications following pancreatic surgery. Intravenous infusions are used in the management of variceal bleeding. Octreotide has been useful in the palliation of the symptoms of malignant bowel obstruction that have not responded to other palliative measures.

Octreotide decreases splanchnic blood flow and inhibits the secretion of serotonin, growth hormone, and the gastroenteropancreatic peptides (gastrin, glucagon, insulin, motilin, pancreatic polypeptide, secretin and vasoactive intestinal peptide [VIP]). Octreotide reduces portal and collateral pressures by inhibiting the release of vasodilatory peptides (including glucagon and VIP), which are increased after gastrointestinal haemorrhage. It also has a direct vasoconstrictive action. Octreotide promotes reabsorption of electrolytes in the gut. In hormone-secreting tumours (eg carcinoid) it improves symptoms by reducing hormone secretion, and it has a direct antitumour effect on solid tumours of the gastrointestinal tract.

Octreotide is usually given subcutaneously to control symptoms of carcinoid tumours and other secretory neoplasms such as VIPomas and glucagonomas. It is also available as a long-acting preparation with octreotide incorporated into microspheres. This formulation is given intramuscularly and provides an extended elevation of octreotide levels—allowing monthly dosing. For patients stabilised on a normal therapeutic dose of subcutaneous octreotide, conversion to the long-acting preparation should be at a dose of 20 mg monthly, and can start the day following the last subcutaneous dose. The dose required for each injection is titrated according to growth hormone levels (in acromegaly) and clinical symptoms.

Adverse effects include a high incidence of cholelithiasis (usually asymptomatic and not requiring treatment), abdominal pain and diarrhoea. Octreotide has an elimination half-life of approximately 1.5 hours and about 30% is excreted renally. Intravenous infusions are well tolerated but blood glucose should be monitored.