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

References

Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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