Glucagon

Dose

How it works

Glucagon is the pancreatic hormone that opposes insulin. It acts on liver glucagon receptors to break down stored glycogen into glucose (glycogenolysis) and to make new glucose (gluconeogenesis). Blood glucose rises within about 10 to 15 minutes. Because it relies on liver glycogen, it fails when those stores are empty. In beta-blocker and calcium channel blocker poisoning, glucagon raises cyclic AMP in heart muscle through its own receptor, bypassing the blocked beta receptors and improving heart rate and contractility.

When it is used

• Severe hypoglycaemia (confused, drowsy, fitting or unable to swallow) when IV access cannot be obtained quickly, in hospital or by trained family members at home.
• Beta-blocker overdose with bradycardia and low BP, as one of several treatments, on poisons advice.
• Occasionally as a smooth-muscle relaxant during radiology (for example, barium studies), or to help pass a food bolus stuck in the oesophagus, though evidence for the latter is weak.

It is not the first choice when IV access is available: IV glucose works faster and more reliably. See Dextrose (glucose).

Cautions

• Ineffective in prolonged fasting, alcohol, liver disease and sulfonylurea-induced lows (needs glycogen stores).
• Nausea and vomiting.

In sulfonylurea overdose, glucagon may also stimulate further insulin release from the pancreas, so the glucose can rise and then fall again. These patients need IV glucose and longer observation.

Contraindications

• Phaeochromocytoma: glucagon can trigger a dangerous catecholamine surge and severe hypertension.
• Insulinoma: it can cause rebound hypoglycaemia.
• Known allergy to glucagon.

Side effects

• Nausea and vomiting (common, especially at the high doses used in poisoning; protect the airway).
• Tachycardia, transient hypertension.
• Low potassium with high-dose infusions.

Interactions

• Increases the effect of warfarin with repeated or high doses.
• Beta-blockers may blunt the rise in heart rate; anticholinergic drugs add to gut slowing.

Monitoring

• Recheck capillary glucose at 10 to 15 minutes. If it is still low, get IV access and give glucose; a second dose of glucagon is rarely helpful.
• Once awake, give oral carbohydrate: fast-acting sugar first, then a longer-acting snack or meal, to replace glycogen and prevent recurrence.
• Keep checking glucose for several hours, and much longer after long-acting insulin or sulfonylurea overdose.
• Target above 4 mmol/L (72 mg/dL).

Pregnancy and breastfeeding

Glucagon does not cross the placenta in significant amounts and can be used to treat severe hypoglycaemia in pregnancy. It is safe during breastfeeding.

Practical tips

• The emergency kit contains a vial of powder and a syringe of water. Inject the water into the vial, swirl gently until clear, draw it back up and inject IM into the thigh, upper arm or buttock. Use it immediately.
• For a child under 25 kg, give half the reconstituted solution.
• Put the patient in the recovery position afterwards because vomiting is common.
• Before discharge, find out why the hypoglycaemia happened: missed meal, excess insulin, alcohol, kidney decline, or a sulfonylurea in an older person.
• Glucagon must be stored as directed (some brands need refrigeration). In hot Pakistani summers, check how families are storing home kits.
• Nasal glucagon exists in some countries but may not be available locally.

See Low blood sugar (hypoglycaemia) and Overdose and poisoning. For exam physiology, read Insulin and glucagon.

Frequently asked questions

Used in these guides

• Bradycardia and heart block
• Low blood sugar (hypoglycaemia)
• Reduced consciousness (the unconscious patient)