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)