Octreotide Acetate

Somatostatin Analog Synthetic octapeptide with somatostatin-like activity

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog SC 10-20 mcg/kg q8-12h Duration: Variable; often long-term for tumor management
Notes: Start at low end and titrate based on clinical response and blood glucose levels. For insulinoma, monitor glucose closely.
Cat SC 10-20 mcg/kg q8-12h Duration: Variable
Notes: Use cautiously; monitor for gastrointestinal side effects.
Horse IV or SC 0.5-1 mg per horse (total dose) q12h Duration: Short-term for research or specific conditions
Notes: Limited data; use only under experimental protocols.
Cattle SC Not established N/A Duration: N/A
Notes: Not recommended for use in food animals due to lack of withdrawal data.
Small Ruminants SC Not established N/A Duration: N/A
Notes: Not recommended.
Rabbit SC Not established N/A Duration: N/A
Notes: Not recommended.
Birds/Poultry Not established Not established N/A Duration: N/A
Notes: Not recommended.
Exotic/Other Not established Not established N/A Duration: N/A
Notes: Not recommended.

Clinical Indications & Species Uses

General Indications
  • Symptomatic treatment of hormone-secreting tumors (e.g., insulinoma, gastrinoma, VIPoma)
  • Control of severe diarrhea and flushing associated with carcinoid syndrome
  • Reduction of growth hormone levels in acromegaly
  • Adjunct in the management of acute variceal bleeding (off-label)
Dog (Canine)
  • Treatment of insulinoma (insulin-secreting pancreatic tumors) to control hypoglycemia
  • Management of acromegaly (rare)
  • Treatment of VIPomas and other gastroenteropancreatic neuroendocrine tumors
  • Control of severe diarrhea associated with certain tumors
  • Adjunct in the management of acute pancreatitis (off-label)
Cat (Feline)
  • Treatment of insulinoma (rare)
  • Management of acromegaly (off-label)
  • Control of diarrhea associated with neuroendocrine tumors

Pharmacology & Mechanism of Action

Drug Class: Somatostatin Analog | Pharmacological Group: Synthetic octapeptide with somatostatin-like activity

Mechanism of Action: Octreotide is a synthetic octapeptide that mimics the actions of endogenous somatostatin. It binds to somatostatin receptors (SSTR2 and SSTR5 predominantly) with high affinity, leading to inhibition of the release of numerous hormones including growth hormone (GH), glucagon, insulin, gastrin, cholecystokinin, vasoactive intestinal peptide (VIP), and secretin. It also reduces gastrointestinal motility, biliary secretion, and splanchnic blood flow. The net effect is a decrease in endocrine and exocrine secretions, which is useful in managing hormone-secreting tumors and certain gastrointestinal disorders.

Pharmacodynamics: Octreotide suppresses GH secretion more potently than somatostatin (45 times more potent) and has a longer duration of action. It inhibits insulin and glucagon release, but with a relatively greater effect on glucagon. It reduces gastric acid secretion, pancreatic enzyme secretion, and intestinal fluid secretion. It also decreases portal venous pressure and splanchnic blood flow, which can be beneficial in cases of acute variceal bleeding. The drug's effects are dose-dependent and reversible upon discontinuation.

⚡ Pharmacokinetics Summary

Absorption: After subcutaneous (SC) or intravenous (IV) administration, octreotide is rapidly and completely absorbed. Peak plasma concentrations occur within 30 minutes after SC injection. Oral bioavailability is very low (<1%) due to extensive degradation in the gastrointestinal tract.
Distribution: The volume of distribution is approximately 0.2-0.3 L/kg. It is widely distributed in tissues, but does not cross the blood-brain barrier significantly. Protein binding is about 65%, primarily to lipoproteins.
Metabolism: Octreotide is metabolized in the liver by hepatic enzymes, with about 30% of the dose undergoing hepatic metabolism. The metabolites are inactive.
Excretion: Approximately 30-40% of the dose is excreted unchanged in the urine, and the remainder is excreted in the bile and feces. Total body clearance is about 160 mL/min.
Half-Life: The elimination half-life is approximately 1.5-2 hours in dogs and cats, but the duration of action is longer (up to 8-12 hours) due to its high affinity for receptors.
Bioavailability: Subcutaneous bioavailability is approximately 100% compared to IV. Oral bioavailability is negligible.
Protein Binding: Approximately 65% bound to plasma proteins.

Available Formulations & Strengths

Injectable Solution 0.05 mg/mL, 0.1 mg/mL, 0.5 mg/mL, 1 mg/mL (SC, IV)
Long-acting Release (LAR) Injectable Suspension 10 mg, 20 mg, 30 mg vials (IM (gluteal muscle))

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to octreotide or any component of the formulation
  • Concurrent use with other somatostatin analogs (unless specifically indicated)
  • Use in animals with known cholelithiasis (gallstones) due to potential for biliary sludge formation
Warnings & Clinical Precautions:
  • Use with caution in animals with diabetes mellitus; octreotide may affect glucose homeostasis (both hypo- and hyperglycemia have been reported).
  • Monitor for signs of hypothyroidism, as octreotide can suppress TSH secretion.
  • May cause bradycardia; use with caution in animals with cardiac disease.
  • Long-term use may lead to gallstone formation; consider periodic ultrasound monitoring.
  • In food animals, withdrawal times are not established; do not use in animals intended for food.
  • Use with caution in animals with renal impairment; dose adjustment may be necessary.
  • Do not administer intravenously as a bolus; infuse slowly if IV route is used.

Adverse Effects & Reactions

Common:

  • Injection site pain or burning
  • Gastrointestinal signs: nausea, vomiting, diarrhea, abdominal discomfort
  • Decreased appetite
  • Changes in blood glucose (hyperglycemia or hypoglycemia)

Serious / Severe:

  • Bradycardia or arrhythmias
  • Cholelithiasis (gallstones) and biliary sludge
  • Hypothyroidism
  • Acute pancreatitis (rare)
  • Allergic reactions (anaphylaxis)

Rare:

  • Hair loss (alopecia)
  • Seizures (in overdose)
  • Hepatotoxicity
  • Thrombocytopenia

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Insulin and oral hypoglycemic agents Octreotide may alter blood glucose levels; dose adjustments of antidiabetic agents may be required. Moderate
Cyclosporine Octreotide may reduce cyclosporine absorption, leading to decreased levels. Moderate
Beta-blockers Additive bradycardia and potential for cardiac conduction disturbances. Moderate
Calcium channel blockers Additive effects on heart rate and blood pressure. Moderate
Diuretics May enhance electrolyte imbalances, particularly hypokalemia. Mild
Other somatostatin analogs Potential for additive effects and increased toxicity. High

Overdose & Toxicity Management

Signs of Toxicity:

  • Severe hypoglycemia or hyperglycemia
  • Bradycardia
  • Gastrointestinal distress (vomiting, diarrhea)
  • Lethargy
  • Hypotension
  • Seizures (in severe cases)

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Monitor blood glucose and cardiac function. Administer IV fluids and electrolytes as needed. For severe bradycardia, atropine may be used. In cases of hypoglycemia, administer dextrose. In cases of hyperglycemia, insulin may be required. Consider gastrointestinal decontamination if recent oral ingestion (though oral bioavailability is low).

Food Animal Withdrawal Times

Not approved for use in food animals. Withdrawal times have not been established. Do not use in animals intended for human consumption.

Storage, Handling & Regulatory Information

Storage Temperature: Store at 2-8°C (refrigerate). Do not freeze.

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light. Store in original carton. For LAR formulation, store at 2-8°C and protect from light. Do not freeze. Once reconstituted, use immediately or discard within 6 hours.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; approved for human use (Sandostatin).

Extra-Label (Off-Label) Use: In the US, octreotide is not FDA-approved for veterinary use; it is used extra-label under the Animal Medicinal Drug Use Clarification Act (AMDUCA). Extra-label use is permitted only by or on the order of a licensed veterinarian within a valid veterinarian-client-patient relationship. For food animals, extra-label use is prohibited if it results in violative residues.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Octreotide is a valuable tool in managing certain endocrine tumors in companion animals, particularly insulinomas in dogs. It can help stabilize blood glucose levels when surgical resection is not possible or as an adjunct to surgery. However, its use is limited by cost, the need for frequent injections, and potential side effects. The long-acting release (LAR) formulation allows for monthly dosing but is more expensive. Clinical monitoring should include blood glucose, thyroid function, and cardiac parameters. Due to the lack of withdrawal data, it should not be used in food animals. Always use the lowest effective dose and titrate based on response. Consider referral to a veterinary oncologist or internal medicine specialist for complex cases.

References & Literature

  • 📚 Plumb's Veterinary Drug Handbook
  • 📚 Papich Veterinary Pharmacology and Therapeutics
  • 📚 Compendium of Veterinary Products (CVP)