Octreotide

Octreotide

Chemical

Octapeptide Somatostatin Analogue

Use

  1. Carcinoid tumours
  2. Variceal bleed
  3. Acromegaly
  4. Hypoglycaemic OD

Presentation

50mcg/mL in 1mL ampoule

Route / Dose

Poor PO absorption

(S/C) 50mcg BD (endocrine tumours)

(IV) 25mcg/hr (variceal bleed)

DoA

Variable, extends up to 12 hours

MoA

  • Binds somatostatin receptor
  • GPCR → ∴inhibits AC
  • Many effects depending on location of receptor

GI

  • More potent inhibitor of GH, glucagon & insulin than somatostatin
  • Inhibits hormone secretion: gastrin, CCK, glucagon, insulin, secretin
  • ↓fluid production by pancreas
  • ↓GI motility
  • Inhibits GB contraction
  • Mesenteric VC ∴↓portal venous P
  • Mesenteric VC ∴↓splanchnic BF

APG

  • Inhibits GH release
  • Inhibits TSH release
  • Inhibits Prolactin release

PD

Metabolic – ↓pancreatic hormone secretion

GI – ↓splanchnic BF & ↓portal venous P

MSK – normalises GH (in Acromegaly)

 NB: vasoactive intestinal peptide tumours → VIP secreting tumours assoc with massive diarrhoea → ∴↓diarrhoea

Carcinoid tumours →↓severe diarrhoea + flushing

OHG O/D → ↓insulin release

PK

A

Poor oral absorption

Given IV

S/C → absorbed quickly & completely

Peaks in 30 mins

D

VD 13L

PPB 65%

M

?metabolism

But prolonged action in renal + liver failure

32% of dose is excreted unchanged in urine

E

30% unchanged in urine

Adverse Effects

Diarrhoea

Nausea/Vomiting

Flatulence

Constipation

Abdominal pain

Hyperglycaemia