Generic Name

Octreotide

Mechanism

Octreotide is a synthetic somatostatin analog that binds to *somatostatin receptors* (SSTR 2, 5) on endocrine and paracrine cells.
• Inhibits secretory hormones: ↓ growth hormone, insulin, glucagon, gastrin, cholecystokinin, and vasoactive intestinal peptide.
• Reduces GI motility and splanchnic blood flow, thereby decreasing abdominal distension and intestinal fluid secretion.
• Antioxidant/reflex hepatic vasoconstriction leads to decreased portal hypertension and variceal bleeding.

This dual action is why octreotide is effective in acromegaly, carcinoid syndrome, and severe GI edema.

Pharmacokinetics

Indications

• Acromegaly – IV bolus 50–100 µg t.i.d. or SC 100–200 µg q12h.
• Carcinoid syndrome – SC 100 µg q8–12h; IV 50–100 µg t.i.d. for breakthrough diarrhea.
• Hepatic portal hypertension – SC 50–100 µg q8h to control variceal bleeding.
• Post‑surgical edema – SC 100 µg q8h to reduce intestinal edema.
• Pancreatic pseudocyst drainage – SC 100 µg q8–12h until symptoms resolve.

Contraindications

• Absolute: *Gallstones* or *chronic cholecystitis* (increased risk of gallstone formation).
• Relative: Severe gastrointestinal disease (e.g., ulcerative colitis) – consider alternative agents.
• Warnings:
• Hypoglycemia – masks insulin, necessitate BG monitoring.
• Cardiovascular – may cause bradycardia or AV block.
• Liver enzymes – can elevate; monitor AST/ALT.
• Retinal – rare *maculopathy* in long‑term use.

Dosing

• Acromegaly:
• *IV*: 50–100 µg t.i.d. for short courses.
• *SC*: 100–200 µg q12h (begin with 100 µg).
• Carcinoid syndrome:
• *SC*: 100 µg every 8–12 h; titrate to symptom control.
• *IV*: 50–100 µg t.i.d. for breakthrough.
• Portal hypertension: 100 µg SC q8h.
• Pseudocyst: 100 µg SC q8–12 h for 7–10 days, taper if improvement.
• Admin tips: Shake vial; inject SC in thigh or abdomen; rotate sites; avoid epicenter injuries.

Adverse Effects

• Common
• GI: nausea, abdominal pain, diarrhea, constipation.
• Flu‑like: chills, fever.
• Local: injection site erythema, induration.
• Serious
• Hypoglycemia (especially with insulin use).
• Gallstones – pancreatitis risk if cholelithiasis present.
• Cardiac: bradycardia, AV block, QT prolongation.
• Liver: hepatotoxicity, cholestatic jaundice.
• Retinopathy: rare, especially in diabetics.

Monitoring

• Blood: Check fasting glucose before doses, especially in insulin‑treated patients.
• Liver: ALT, AST, bilirubin every 4–6 weeks for chronic therapy.
• Gallbladder: Ultrasound if RUQ pain, sludge, or gallstone suspicion.
• Cardiac: ECG if bradyarrhythmia develops; monitor QTc.
• Infusion rates: Ensure IV rates not > 10 µg/min to avoid respiratory depression.

Clinical Pearls

• Pulse‑Oximetry: If IV dosing > 10 µg/min, a 0.5 % desaturation may occur; pre‑medicate with 2 % lidocaine in the infusion line.
• Masking of Hypoglycemia: Octreotide can blunt glucagon release; monitor glucose *every 4 h* when used with insulin or sulfonylureas.
• Subcutaneous Rotation: Iatrogenic chronic* molecule should be rotated to prevent local tissue necrosis; alternate thigh/abdomen.
• Dosing for Younger Children: Weight‑based dosing (0.1 mg/kg) has shown similar efficacy; adjust based on serum insulin‑like growth factor‑1 levels.
• Drug‑Drug Interactions: Use with *beta‑blockers* cautiously; hypoglycemia can be more pronounced.
• Long‑Term Therapy: Consider injection site screening for erythema or induration at 6‑month intervals; switch to IV or SC as patient tolerates.

Key Takeaway: Octreotide’s potent SSTR‑2/5 activation makes it a cornerstone for hormone‑driven tumors and portal hypertension, but vigilant glucose, hepatic, and cardiac monitoring are essential for safe use.