indication

For treatment of acromegaly and reduction of side effects from cancer chemotherapy

pharmacology

Octreotide exerts pharmacologic actions similar to the natural hormone, somatostatin. It is an even more potent inhibitor of growth hormone, glucagon, and insulin than somatostatin. Like somatostatin, it also suppresses leuteinizing hormone (LH) response to GnRH, decreases splanchnic blood flow, and inhibits release of serotonin, gastrin, vasoactive intestinal peptide, secretin, motilin, and pancreatic polypeptide. Octreotide has been used to treat the symptoms associated with metastatic carcinoid tumors (flushing and diarrhea), and Vasoactive Intestinal Peptide (VIP) secreting adenomas (watery diarrhea). Octreotide substantially reduces and in many cases can normalize growth hormone and/or IGF-1 (somatomedin C) levels in patients with acromegaly.

mechanism of action

Octreotide binds to somatostatin receptors. These receptors are coupled via pertussis toxin sensitive G proteins which lead to inhibition of adenylyl cyclase. Octreotide binding to these receptors also stimulates phosphotyrosine phosphatase and activation of the Na(+)/H(+) exchanger via pertussis toxin insensitive G proteins.

route of elimination

About 32% of the dose is excreted unchanged into the urine.

drug interactions

Artemether: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Cyclosporine: Octreotide decreases the effect of cyclosporine

Lumefantrine: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Quinupristin: This combination presents an increased risk of toxicity

Tacrolimus: Additive QTc-prolongation may occur increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution.

Thiothixene: May cause additive QTc-prolonging effects. Increased risk of ventricular arrhythmias. Consider alternate therapy. Thorough risk:benefit assessment is required prior to co-administration.

Toremifene: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Consider alternate therapy. A thorough risk:benefit assessment is required prior to co-administration.

Trimipramine: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution.

Voriconazole: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Vorinostat: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Ziprasidone: Additive QTc-prolonging effects may increase the risk of severe arrhythmias. Concomitant therapy is contraindicated.

Zuclopenthixol: Additive QTc prolongation may occur. Consider alternate therapy or use caution and monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).