What is Octreotide?
Octreotide is a synthetic (man-made) octapeptide that mimics the action of the natural hormone somatostatin [1.4.1]. Because it is more resistant to metabolic degradation, it has a much longer duration of action than its natural counterpart [1.4.4]. Marketed under brand names like Sandostatin®, Sandostatin LAR® Depot, and Mycapssa®, it functions as a somatostatin analog [1.2.2, 1.3.2]. Its primary mechanism involves binding to somatostatin receptors, which are prevalent in the pituitary gland and the gastrointestinal tract. This binding action inhibits the secretion of numerous hormones, including growth hormone (GH), insulin, glucagon, and various hormones of the gastroenteropancreatic endocrine system like vasoactive intestinal peptide (VIP) and serotonin [1.4.1, 1.4.4]. By blocking the release of these hormones, octreotide effectively manages the symptoms and complications arising from their overproduction [1.2.2].
FDA-Approved Indications: What Does Octreotide Treat?
The U.S. Food and Drug Administration (FDA) has approved octreotide for several specific conditions related to hormone over-secretion [1.2.1, 1.3.4].
Acromegaly
Acromegaly is a rare hormonal disorder caused by the pituitary gland producing excessive amounts of growth hormone (GH) in adults, leading to the overgrowth of bones in the hands, feet, and face [1.2.3]. Octreotide is a first-line medical treatment for patients with persistent disease after surgery [1.3.4]. It works by suppressing the pituitary's release of GH, which in turn normalizes levels of Insulin-Like Growth Factor-1 (IGF-1), the substance responsible for many of the disease's effects [1.2.2, 1.2.4].
Symptomatic Control of Neuroendocrine Tumors (NETs)
Octreotide is highly effective at managing the debilitating symptoms caused by certain types of metastatic neuroendocrine tumors, although its effect on tumor size itself has not been definitively determined for these cancers [1.3.4, 1.10.1].
- Carcinoid Syndrome: This syndrome is associated with carcinoid tumors and is characterized by severe diarrhea and episodic skin flushing [1.2.3]. Octreotide inhibits the tumor's overproduction of substances like serotonin, providing significant relief from these symptoms [1.2.1, 1.4.4].
- Vasoactive Intestinal Peptide Tumors (VIPomas): These rare pancreatic tumors secrete excessive amounts of vasoactive intestinal peptide (VIP), leading to large volumes of watery diarrhea and subsequent dehydration and electrolyte imbalances [1.2.2, 1.2.3]. Octreotide directly inhibits the release of VIP, controlling the severe diarrhea [1.2.1].
Common Off-Label Uses
Beyond its approved indications, clinicians use octreotide "off-label" to manage a variety of other conditions. These uses are often supported by clinical evidence but have not gone through the formal FDA approval process for that specific condition [1.3.1].
Some prominent off-label uses include:
- Bleeding Esophageal Varices: In patients with liver cirrhosis, octreotide is often a first-choice treatment to manage acute bleeding from esophageal varices. It works by reducing blood flow to the gut and lowering pressure around the liver [1.2.2, 1.3.2].
- Refractory Diarrhea: Octreotide is used to treat persistent and severe diarrhea associated with chemotherapy, HIV/AIDS, or graft-versus-host disease [1.3.1].
- Hypoglycemia: It can be used to treat refractory hypoglycemia (low blood sugar), particularly when caused by sulfonylurea overdose or congenital hyperinsulinism in neonates [1.3.1, 1.3.2].
- Dumping Syndrome: This medication can help manage the symptoms that occur after gastric surgery, known as dumping syndrome [1.3.1].
- Pancreatitis Complications: It is sometimes used to help manage complications from pancreatitis or pancreatic surgery [1.3.1, 1.11.1].
Octreotide Formulations: Short-Acting vs. Long-Acting
Octreotide is available in immediate-release (short-acting) and long-acting release (LAR) formulations, which serve different purposes in treatment [1.6.1].
| Feature | Short-Acting (Sandostatin®) | Long-Acting (Sandostatin LAR® Depot) |
|---|---|---|
| Administration | Subcutaneous (under the skin) or Intravenous (IV) injection [1.7.1, 1.7.2] | Intramuscular (IM) injection into the gluteal muscle [1.6.1, 1.7.4] |
| Dosing Frequency | 2 to 4 times per day [1.2.2] | Once every 4 weeks [1.7.1] |
| Primary Use Case | Initial treatment to assess tolerance and efficacy; management of breakthrough symptoms [1.6.1] | Long-term maintenance therapy for patients who have responded well to the short-acting form [1.3.4] |
| Onset of Action | Rapid, within 30 minutes [1.11.1] | Slow release; therapeutic levels are reached over time, requiring overlap with the short-acting form initially [1.3.4, 1.6.1] |
| Self-Administration | Often administered by the patient at home [1.7.1] | Must be administered by a healthcare provider [1.6.1, 1.7.4] |
Potential Side Effects and Monitoring
While effective, octreotide treatment requires careful monitoring due to its range of potential side effects [1.13.3].
Common Side Effects
The most frequently reported side effects are related to the gastrointestinal system and often improve over time [1.2.2, 1.5.1].
- Diarrhea, abdominal pain, nausea, and gas [1.5.1]
- Pain, redness, or swelling at the injection site [1.5.1]
- Headache and dizziness [1.5.1]
Serious Side Effects & Required Monitoring
Octreotide can impact several body systems, necessitating regular monitoring by a healthcare provider [1.13.3].
- Gallbladder Issues: Octreotide can lead to the formation of gallstones (cholelithiasis) or biliary sludge in a significant number of patients [1.5.1, 1.5.3]. Periodic ultrasound monitoring of the gallbladder is often recommended [1.3.4].
- Blood Sugar Changes: The medication can cause both hyperglycemia (high blood sugar) and hypoglycemia (low blood sugar) by altering the balance of insulin and glucagon [1.5.1, 1.12.1]. Blood glucose levels must be monitored, especially in patients with diabetes [1.13.2].
- Thyroid Function: It can suppress the secretion of Thyroid Stimulating Hormone (TSH), potentially leading to hypothyroidism. Baseline and periodic thyroid function tests are necessary during chronic therapy [1.3.4, 1.5.1].
- Cardiac Effects: Bradycardia (slow heart rate) and other conduction abnormalities can occur. Patients with underlying heart conditions require careful monitoring [1.5.1, 1.13.2].
- Vitamin B12 Levels: Long-term use can decrease vitamin B12 levels, so levels may be monitored periodically [1.3.4, 1.12.1].
Conclusion
Octreotide is a powerful medication that plays a critical role in the field of endocrinology and oncology. By mimicking the body's native somatostatin, it effectively addresses conditions driven by hormone overproduction. Its primary FDA-approved uses for treating acromegaly and managing the severe symptoms of carcinoid syndrome and VIPomas have significantly improved patients' quality of life [1.2.1, 1.2.2]. Furthermore, its broad range of off-label applications, from controlling variceal bleeding to managing complex forms of diarrhea, highlights its versatility [1.3.1, 1.3.2]. Treatment requires careful selection between short- and long-acting formulations and diligent monitoring for potential side effects, particularly those affecting the gallbladder, blood sugar, and thyroid function, to ensure both safety and efficacy [1.13.3].
For more information, consult a healthcare professional. An authoritative resource on this medication is available from the National Library of Medicine. [1.7.1, 1.7.4]
