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GLUCAGON

CLASS

Antihypoglycaemic, hormone

PRESENTATION

White lyophilised powder

Formulations

  • 1mg/1U prefilled syringe
  • 1mg/1U powder for reconstitution

INDICATIONS & DOSING

Hypoglycaemia (particularly in the setting of insulin or oral hypoglycaemic agents)

  • Adult, paediatric >25kg; 1mg IV/SC/IM bolus
  • Paediatric <25kg; 20-30mcg/kg or 500mcg IV/SC/IM bolus

Facilitation of instrumentation of gastrointestinal tract

  • Adult; 0.5-2mg IV bolus

Shock states in the setting of beta-blockade or catecholamine unresponsiveness (most commonly anaphylaxis)

  • Adult; 1-5mg IV bolus, repeat if necessary

Antidote; beta-blocker or calcium channel overdose (largely historical)

  • Adult; 5-10mg IV bolus, repeat if necessary plus infusion, infusion 1-5mg/hr
  • Paediatric; 50-100mcg/kg IV bolus, repeat if necessary, infusion 100mcg/kg/hr

PRACTICALITIES

Administration

  • Reconstitute powder formulation with pre-drawn syringe or 5% dextrose

Practice tips

  • Glucagon should generally be second-line therapy for hypoglycaemia after IV dextrose
  • Hyperglycaemic effect requires hepatic glycogen stores – not effective in starvation
  • Supplement oral carbohydrates after use to restore hepatic glycogen and prevent secondary hypoglycaemia
  • Not effective in setting of adrenal insufficiency, chronic hypoglycaemia, alcohol induced hypoglycaemia
  • Monitor for recrudescence of hypoglycaemia in managing sulfonurea-induced hypoglycaemia, IV glucose appropriate
  • Proximal gastrointestinal tract more sensitive requiring lower dose range for effect

PHARMACOKINETICS

Onset

  • IV; 1 minute (increase in BSL <10 minutes)
  • IM; 10 minutes

Duration of action

  • IV; duration 60-90 minutes (BSL), 5-20 mins (GI effects)
  • IM; duration 10-40 mins 

Metabolism, elimination

Mixed hepatic metabolism, renal elimination and enzymatic degradation

MECHANISM

Stimulation of glucagon receptors, increase in cAMP concentration

DESIRED CLINICAL EFFECTS

Cardiovascular

  • Positive inotropy > chronotropy via increase in intracellular cAMP independent of beta-receptors or calcium flux, and stimulation of catecholamine release 

Gastrointestinal

  • Decreases gastrointestinal motility and tone, relaxes gastrointestinal tract and sphincters facilitating instrumentation

Endocrine

  • Raises blood sugar via stimulation of hepatic glycogenolysis and gluconeogenesis, lipolysis, proteolysis, ketogenesis

OTHER CLINICAL EFFECTS, ADVERSE EFFECTS & TOXICITIES

Cardiovascular

  • Tachycardia, hypertension
  • Hypertensive crisis in setting of pheochromocytoma 

Renal & electrolytes

  • Initial hyperkalaemic effect, followed by prolonged hypokalaemic effect due to stimulation of insulin release

Gastrointestinal

  • Nausea, vomiting
  • Inhibits gastric and pancreatic secretions

Endocrine

  • Encourages insulin, growth hormone release

CONSIDERATIONS

Precautions

  • Pheochromocytoma; hypertensive crisis secondary to catecholamine release
  • Insulinoma; hypoglycaemia due to stimulation of insulin release
  • Glucagonoma; hyperglycaemia, haemodynamic instability

Obstetric 

ADEC category C

Drug interactions

  • Indomethacin; inhibits effect on blood glucose level, potential for paradoxical hypoglycaemia
  • Warfarin; potentiates anticoagulant effect

REFERENCES

Drug information has been compiled from multiple sources including

  • Drugs in Anaesthesia and Intensive Care (Scarth & Smith)
  • Micromedex (IBM)
  • BJA Education (Oxford Academic)
  • Pharmacology for Anaesthesia and Intensive Care (Cambridge)
  • Australian Prescriber (NPS MedicineWise)

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