Pharmacology · Somatostatin analogues
Octreotide !
A long-acting copy of somatostatin, given by injection. It lowers growth hormone in acromegaly and controls diarrhoea from hormone-secreting tumours.
Updated 2026-11-01
The figure shows octreotide itself (a short cyclic peptide chain) bound to the human SSTR2 receptor with its G protein (cryo-EM).
Mechanism of action
Octreotide is an eight-amino-acid cyclic analogue of somatostatin that resists breakdown, so it acts for hours instead of minutes. It binds mainly SSTR2 (and SSTR5), Gi-coupled receptors that lower cAMP and calcium entry. It inhibits growth hormone, insulin, glucagon, serotonin, gastrin and VIP secretion, slows gut motility and gallbladder contraction, and lowers splanchnic and portal blood flow.
- Octreotide binds SSTR2 on pituitary, gut and tumour cells
- Gi lowers cAMP and calcium entry
- Secretion of GH, serotonin, VIP and gut hormones falls
- Splanchnic and portal blood flow decrease
Pharmacokinetics
- Absorption
- Given subcutaneously or IV; long-acting depot forms are injected IM
- Half-life
- Much longer than natural somatostatin, which lasts only minutes
Indications
- Acromegaly when surgery, radiation or other drugs are not enough Pituitary adenoma →
- Severe diarrhoea and flushing of metastatic carcinoid tumours Carcinoid syndrome →
- Watery diarrhoea from VIP-secreting tumours (VIPomas)
- Acute variceal bleeding in cirrhosis, to lower portal pressure Upper gastrointestinal bleeding →
Adverse effects
Common
- Diarrhoea, nausea, abdominal pain and gas
- Pain at the injection site
- Fatty stools (steatorrhoea)
- Low or high blood glucose
Contraindications
- Hypersensitivity to octreotide or its components
Key interactions
- Ciclosporin
- Lower ciclosporin levels, with risk of transplant rejection
- Insulin and oral antidiabetic drugs
- Glucose may rise or fall; doses may need adjusting
- Beta-blockers and other drugs that slow the heart
- Additive bradycardia
- Bromocriptine
- Higher bromocriptine levels
What is monitored
- Blood glucose
- Heart rate, and ECG during IV use
- Gallbladder (ultrasound if symptoms)
- Thyroid function
- Growth hormone and IGF-1 in acromegaly
Administration and safety
- Immediate-release solution is given subcutaneously or IV; the depot suspension is IM only
- Subcutaneous sites are rotated
- Look-alike risk between immediate-release and depot products: confirm the product and route
Nursing care
- Check glucose, especially in people with diabetes
- Monitor heart rate; during IV infusion, cardiac monitoring
- Ask about right upper abdominal pain, fever or jaundice (gallstones)
- Teach self-injection technique and site rotation
Pregnancy and breastfeeding
Data in pregnancy are limited; it is used only when the benefit justifies it. By lowering GH it may restore fertility in women with acromegaly.
Test yourself
Think of the answer, then tap the question to see it.
Why does octreotide help in acute variceal bleeding?
It lowers splanchnic and portal blood flow, reducing variceal pressure while endoscopic treatment is arranged.
Which long-term complication of octreotide involves the gallbladder?
Gallstones and biliary sludge, because gallbladder contraction is inhibited.
Why can octreotide cause both hypo- and hyperglycaemia?
It suppresses both insulin and glucagon; the net effect on glucose depends on which falls more.
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Octreotide Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2020); DailyMed - OCTREOTIDE ACETATE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 62 (McGraw Hill, 2025).
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Representative model, for educational purposes only.