glucagon
antihypoglycemic agent· Brands: Glucagen, GlucaGen, HypoKit, Baqsimi, GlucagonIMINHIVSC
Mechanism of action
Glucagon is a peptide hormone that raises blood glucose by promoting hepatic glycogenolysis and gluconeogenesis. It binds to glucagon receptors on hepatocytes, activating adenylate cyclase and increasing cAMP, which leads to glycogen breakdown and glucose release. It also inhibits glycogen synthesis and stimulates gluconeogenesis.
Pharmacokinetics
After administration, glucagon is rapidly absorbed, with peak plasma concentrations occurring within 30 minutes. It has a short half-life of approximately 5 to 10 minutes, requiring repeated dosing or infusion for sustained effect. Metabolism occurs in the liver and kidney. Excretion is via renal pathways.
Indications & dosing
Severe hypoglycemia in adults
If no response after 15 min, repeat once; give oral glucose when conscious.
- adult · IM: 1 mg Single dose · If no response after 15 min, repeat once; give oral glucose when conscious.
Severe hypoglycemia in children
Weight-based: 0.5 mg for <25 kg, 1 mg for ≥25 kg.
- pediatric · IM: 0.5–1 mg Single dose · Weight-based: 0.5 mg for <25 kg, 1 mg for ≥25 kg.
Diagnostic aid in radiology
Administer IV to relax the gastrointestinal tract during imaging.
- adult · IV: 0.5–1 mg Single dose · Administer IV to relax the gastrointestinal tract during imaging.
Beta-blocker overdoseoff-label
Followed by infusion if needed; monitor heart rate and blood pressure.
- adult · IV: 5–10 mg Initial dose · Followed by infusion if needed; monitor heart rate and blood pressure.
Contraindications & precautions
- Phaeochromocytoma · Glucagon may stimulate catecholamine release and cause severe hypertension.
- Insulinoma · Risk of rebound hypoglycaemia due to insulin release.
- Known hypersensitivity to glucagon · Avoid in patients with a history of allergic reactions to glucagon.
- Use with caution in patients with cardiac disease, as glucagon can cause arrhythmias and hypertension.
- May be ineffective in patients with depleted glycogen stores (e.g., prolonged fasting, severe hepatic disease); consider alternative treatment.
- Caution in patients with adrenal insufficiency, as they may not respond adequately.
- Caution in patients taking beta-blockers, as the usual sympathomimetic response may be blunted.
Adverse effects
- Nausea
- Vomiting
- Tachycardia
- Hypertensionserious
- Arrhythmiasserious
- Allergic reactionsserious
- Rebound hypoglycaemiaserious
Monitoring, pregnancy & toxicity
- Blood glucose · Check at 15-20 minutes after administration
- Signs of hypoglycaemia · Observe for resolution of symptoms
- Nausea and vomiting · Assess for gastrointestinal adverse effects
- Pregnancy: Glucagon is safe to use during pregnancy for the immediate treatment of severe hypoglycaemia. It does not cross the placenta and poses no known fetal risk.
- Toxicity: Nausea and vomiting · Supportive care; antiemetics if needed
- Toxicity: Hyperglycaemia · Monitor blood glucose; treat with insulin if persistent
- Toxicity: Hypokalaemia · Monitor electrolytes; supplement if needed
- Toxicity: Hypotension in severe overdose · IV fluids and supportive measures
Clinical notes
Glucagon is used to treat severe hypoglycaemia in diabetic patients who are unconscious or unable to take oral glucose. It may also be used in beta-blocker overdose or as a diagnostic aid. Administer as a standard dose of 1 mg intramuscularly or subcutaneously; onset of action is within 5 to 15 minutes. It should be used with caution in patients with phaeochromocytoma or insulinoma. Patients should be monitored for recurrence of hypoglycaemia after initial response, as glycogen stores may be depleted. Ensure adequate glucose intake after recovery to prevent relapse.
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BNF; local formulary