Glucagon

Glucagon

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Glucagon is a pancreatic polypeptide. It increases intracellular cyclic AMP concentrations, which results in release of cAMP-dependent protein kinase, activating calcium channels, thus improving myocardial contractility and increasing the heart rate. These effects are independent of ß-adrenoceptor cardiac effects.

The major out-of-hospital use of glucagon is as a subcutaneous or intramuscular injection to reverse insulin-induced hypoglycaemia.

Use in toxicology

Glucagon is used intravenously as second-line therapy in beta blocker and calcium channel blocker overdose to treat:

bradycardia or conduction impairment resistant to other therapeutic manoeuvres such as atropine, isoprenaline and/or cardiac pacing

hypotension unresponsive to fluid challenges.

The dose used in the toxicology setting is much larger than that used in management of hypoglycaemia. A bolus dose is followed by a continuous infusion. Glucagon is currently only available in Australia in 1 mg vials or prefilled syringes. For toxicological presentations, it may be necessary to seek additional supplies from nearby hospitals. Most states have an Emergency and Life-saving Medications register that lists hospitals that may be able to assist with supply. The commercial diluent currently available in Australia can be used for reconstitution, as it does not contain phenol, unlike the 10 mg vials available overseas. Otherwise, water for injection or sodium chloride 0.9% may be used for reconstitution.

The onset of action of glucagon in the setting of beta blocker or calcium channel blocker overdose is within 1 to 2 minutes, and effects persist for 10 to 20 minutes. Glucagon is generally well-tolerated, but high doses can cause significant nausea. Patients should be monitored for hyperglycaemia.