Pharm 101: Octreotide
Class
Somatostatin analogue
Pharmacodynamics
- Long-acting somatostatin analogue
- Reduces splanchnic blood flow and portal venous pressure by unknown mechanisms (hence reduces variceal pressures)
- Inhibits endocrine and paracrine factor secretion, including insulin, glucagon, gastrin, GH and TSH
- 45 times more potent than somatostatin at inhibiting GH, but only twice as potent in reducing insulin secretion
- Hyperglycaemia therefore rarely occurs
Pharmacokinetics
- IV, IM, SC administration
- Half-life 80 minutes
- Hepatic metabolism (30-40%)
- 20% excreted unchanged by kidney
Clinical uses
- Acute variceal bleeding:
- IV 50mcg bolus then 50mcg/hour infusion
- Infusion is required because of short half-life
- Sulphonylurea overdose
- Reduction of symptoms of hormone secreting tumours e.g. pituitary and carcinoid tumours (long-acting injections)
Adverse effects
- GI upset
- Biliary: gallstones in 25% after 6 months (annual incidence of symptomatic gallstones 1%)
- CVS: sinus bradycardia 25%, conduction disturbances 10%
- Pain at site of injection
- B12 deficiency with long-term use
Further reading
- Nickson C. Gastrointestinal Haemorrhage. LITFL
References
- Katzung BG. Basic and Clinical Pharmacology. 14e. 2018: 672-673, 683
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Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Co-creator of the LITFL ECG Library. Twitter: @rob_buttner