Usage
Somatostatin is prescribed for the symptomatic treatment of hormone-secreting gastrointestinal and pancreatic tumors, including carcinoid tumors, VIPomas, and glucagonomas. It’s also used to manage acute bleeding from esophageal varices, peptic ulcers, and gastritis, as well as complications following pancreatic surgery. Additionally, it can be used as an adjunctive treatment in diabetic ketoacidosis. Pharmacologically, somatostatin is classified as a growth hormone-inhibiting hormone and belongs to the somatostatin and somatostatin analog class. It works by mimicking the natural hormone somatostatin, which inhibits the release of various hormones and peptides, including growth hormone, insulin, glucagon, gastrin, and secretin.
Alternate Names
Somatostatin is also known as growth hormone-inhibiting hormone (GHIH). Brand names include Sandostatin, Sandostatin LAR Depot, and Stilamin.
How It Works
Pharmacodynamics: Somatostatin binds to specific somatostatin receptors (SSTRs), primarily SSTR2 and SSTR5, which are G protein-coupled receptors located on the surface of various cells throughout the body. Activation of these receptors leads to inhibition of adenylate cyclase, reduction of intracellular cAMP, and modulation of calcium and potassium channels, ultimately suppressing the secretion of numerous hormones and peptides.
Pharmacokinetics: Somatostatin, when administered intravenously, is rapidly distributed and has a short half-life of approximately 1-3 minutes. It’s metabolized by peptidases in various tissues, including the liver and kidneys, and excreted primarily in the urine. Subcutaneous administration results in slower absorption and a slightly longer half-life. Long-acting formulations (e.g., Sandostatin LAR Depot) provide sustained release over several weeks.
Mode of Action: Somatostatin’s primary mechanism involves binding to SSTRs, inhibiting hormone release. The specific effects depend on the target tissue and the SSTR subtypes involved. For example, in acromegaly, it reduces growth hormone secretion; in carcinoid tumors, it inhibits the release of serotonin and other vasoactive substances.
Elimination: Somatostatin is rapidly cleared by peptidase-mediated metabolism, with excretion primarily through the kidneys and to a lesser extent, the liver.
Dosage
Standard Dosage
Adults:
Standard dosages vary based on the indication and formulation. For acromegaly, initial doses of Sandostatin (immediate release) range from 50 mcg subcutaneously three times daily, titrated up to 500 mcg three times daily. Sandostatin LAR Depot (long-acting) is administered intramuscularly at 20 mg every four weeks, adjustable to 10-30 mg based on response. For carcinoid tumors and other hormone-secreting GI tumors, the initial dose is 100-600 mcg/day subcutaneously, divided into 2-4 doses, which can be adjusted based on the clinical response and tolerability.
Children:
Dosage in children is determined by the physician based on weight and the specific condition being treated.
Special Cases:
- Elderly Patients: Dose adjustment may be necessary due to age-related decline in renal and hepatic function.
- Patients with Renal Impairment: Dose adjustments are generally not required, as renal impairment doesn’t significantly affect octreotide pharmacokinetics.
- Patients with Hepatic Dysfunction: Dose reduction may be needed in patients with liver cirrhosis due to increased half-life.
- Patients with Comorbid Conditions: Careful monitoring is required in patients with diabetes, gallbladder disease, or cardiovascular conditions.
Clinical Use Cases:
Dosing for specific conditions is addressed in the adult dosing section above.
Dosage Adjustments:
Dosage is adjusted based on individual patient response, tolerance, and therapeutic goals. It is crucial to monitor hormone levels (e.g., GH, IGF-1) and clinical symptoms to optimize treatment.
Side Effects
Common Side Effects:
Nausea, vomiting, diarrhea, abdominal pain, injection site reactions, headache, dizziness, and alterations in blood glucose levels (hypoglycemia or hyperglycemia).
Rare but Serious Side Effects:
Gallstones, pancreatitis, bradycardia, conduction abnormalities, and hypersensitivity reactions.
Long-Term Effects:
Gallbladder sludge or stones can develop with long-term use.
Adverse Drug Reactions (ADR):
Severe hypersensitivity reactions (anaphylaxis), severe bradycardia or heart block, and acute pancreatitis.
Contraindications
Hypersensitivity to somatostatin or any component of the formulation.
Drug Interactions
Somatostatin can interact with cyclosporine, cimetidine, and drugs affecting glucose metabolism (insulin, oral hypoglycemics). It can also impact the absorption of oral medications due to effects on gastrointestinal motility.
Pregnancy and Breastfeeding
Limited data suggest potential fetal risks, so somatostatin should be used during pregnancy only if the benefits clearly outweigh the risks. Its presence in breast milk is unknown, making its use during breastfeeding generally inadvisable.
Drug Profile Summary
- Mechanism of Action: Inhibits hormone and peptide secretion by binding to somatostatin receptors.
- Side Effects: Nausea, vomiting, diarrhea, abdominal pain, injection site reactions, glucose alterations.
- Contraindications: Hypersensitivity to somatostatin.
- Drug Interactions: Cyclosporine, cimetidine, drugs affecting glucose metabolism.
- Pregnancy & Breastfeeding: Use with caution; potential fetal risks; unknown in breast milk.
- Dosage: Varies based on indication and formulation; see detailed dosage section.
- Monitoring Parameters: Hormone levels (e.g., GH, IGF-1), tumor markers, blood glucose, liver function tests, and cardiac function.
Popular Combinations
Somatostatin analogs are sometimes used in combination with other therapies, like interferon or targeted radionuclide therapy, for the treatment of neuroendocrine tumors.
Precautions
Carefully monitor patients with diabetes, gallbladder disease, or cardiovascular conditions. Adjust dosage in patients with hepatic impairment.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Somatostatin?
A: Dosages vary significantly depending on the indication and formulation. See the detailed dosage section for specific recommendations.
Q2: What are the common side effects of Somatostatin?
A: Common side effects include nausea, vomiting, diarrhea, abdominal pain, injection site reactions, and changes in blood glucose levels.
Q3: How does Somatostatin work?
A: Somatostatin mimics the natural hormone somatostatin by binding to somatostatin receptors and inhibiting the release of various hormones and peptides.
Q4: Can Somatostatin be used during pregnancy?
A: Limited data exist on its use in pregnancy, suggesting potential fetal risks. Use only if the benefits clearly outweigh the risks.
Q5: Is Somatostatin safe for breastfeeding mothers?
A: Its presence in breast milk is unknown. Its use during breastfeeding is generally discouraged.
Q6: What are the contraindications for Somatostatin use?
A: Hypersensitivity to somatostatin is the primary contraindication.
Q7: Are there any significant drug interactions with Somatostatin?
A: It can interact with cyclosporine, cimetidine, and medications affecting glucose metabolism. It may also affect the absorption of oral drugs.
Q8: What are the long-term effects of using Somatostatin?
A: Gallbladder sludge or stones can occur with prolonged use. Regular monitoring is necessary.
Q9: What should be monitored in patients receiving Somatostatin?
A: Key monitoring parameters include hormone levels (e.g., GH, IGF-1), tumor markers, blood glucose, liver function tests, and cardiac function.
Q10: How is Somatostatin administered?
A: It can be administered intravenously, subcutaneously, or intramuscularly, depending on the specific formulation and clinical indication.
This information is current as of February 17, 2025, and is intended for use by qualified medical professionals. Always consult with up-to-date resources and individual patient factors when making treatment decisions.
