Glucagon

Hormone Pancreatic hormone; Antihypoglycemic agent

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog IV, IM, SC Emergency hypoglycemia: 0.03-0.1 mg/kg (max 1 mg) IV; if no IV access, IM or SC May repeat in 15-20 minutes if no response; continuous infusion: 0.01-0.04 mg/kg/hour Duration: As needed until blood glucose stabilizes
Notes: For GI motility: 0.1 mg/kg IV as a single dose; may be repeated.
Cat IV, IM, SC Emergency hypoglycemia: 0.03-0.1 mg/kg IV (max 1 mg); if no IV access, IM or SC May repeat in 15-20 minutes; continuous infusion: 0.01-0.04 mg/kg/hour Duration: As needed until blood glucose stabilizes
Notes: For GI motility: 0.1 mg/kg IV as a single dose.
Horse IV Neonatal foal hypoglycemia: 0.1-0.2 mg/kg IV slowly May repeat as needed Duration: Until blood glucose normalizes
Notes: For ileus: 0.1 mg/kg IV as a single dose; monitor for side effects.
Cattle IV, IM Neonatal calf hypoglycemia: 0.1-0.2 mg/kg IV or IM May repeat as needed Duration: Until blood glucose normalizes
Notes: Not commonly used; ensure adequate glucose support.
Small Ruminants IV, IM Neonatal hypoglycemia: 0.1-0.2 mg/kg IV or IM May repeat as needed Duration: Until blood glucose normalizes
Notes: Not commonly used; ensure adequate glucose support.
Rabbit IV, IM, SC Emergency hypoglycemia: 0.1-0.2 mg/kg IV or IM May repeat as needed Duration: Until blood glucose normalizes
Notes: Use with caution; monitor blood glucose closely.
Exotic (ferrets, small mammals) IV, IM, SC Emergency hypoglycemia: 0.1-0.2 mg/kg IV or IM May repeat as needed Duration: Until blood glucose normalizes
Notes: Use with caution; monitor blood glucose closely.

Clinical Indications & Species Uses

General Indications
  • Emergency treatment of hypoglycemia
  • Diagnostic aid for gastrointestinal motility disorders
  • Treatment of beta-blocker or calcium channel blocker overdose
Dog (Canine)
  • Emergency treatment of severe hypoglycemia (e.g., insulin overdose, insulinoma)
  • Diagnostic aid for gastrointestinal motility disorders (e.g., ileus, pylorospasm)
  • Adjunct in treatment of beta-blocker or calcium channel blocker overdose
Cat (Feline)
  • Emergency treatment of severe hypoglycemia (e.g., insulin overdose)
  • Diagnostic aid for gastrointestinal motility disorders
Horse (Equine)
  • Treatment of hypoglycemia in neonatal foals
  • Adjunct in management of colic with ileus
Cattle (Bovine)
  • Treatment of hypoglycemia in neonatal calves
Small Ruminants (Sheep / Goat)
  • Treatment of hypoglycemia in neonates
Rabbit & Small Mammals
  • Emergency treatment of hypoglycemia
Exotic & Other Species
  • Emergency treatment of hypoglycemia in small mammals (e.g., ferrets, guinea pigs)

Pharmacology & Mechanism of Action

Drug Class: Hormone | Pharmacological Group: Pancreatic hormone; Antihypoglycemic agent

Mechanism of Action: Glucagon is a polypeptide hormone produced by alpha cells of the pancreatic islets. It acts primarily on the liver to stimulate glycogenolysis, converting glycogen to glucose, and to promote gluconeogenesis, thereby increasing blood glucose levels. It also has positive inotropic and chronotropic effects on the heart, and relaxes smooth muscle of the gastrointestinal tract. Its effects are mediated via G-protein coupled glucagon receptors, leading to activation of adenylate cyclase and increased cyclic AMP.

Pharmacodynamics: Glucagon raises blood glucose concentration within minutes of administration. It also inhibits gastric and pancreatic secretions, decreases gastrointestinal motility, and increases myocardial contractility. In veterinary medicine, it is used for emergency treatment of severe hypoglycemia, as a diagnostic aid in gastrointestinal motility disorders, and as a positive inotrope in certain cardiac emergencies.

⚑ Pharmacokinetics Summary

Absorption: After subcutaneous or intramuscular injection, glucagon is absorbed rapidly. Oral administration is ineffective due to degradation in the gastrointestinal tract.
Distribution: Glucagon is distributed throughout the body, with highest concentrations in the liver and kidneys. It crosses the placenta minimally.
Metabolism: Glucagon is rapidly degraded in the liver, kidneys, and plasma by proteolytic enzymes. Its half-life is short.
Excretion: Metabolites are excreted in the urine and bile. A small amount of intact glucagon is excreted in urine.
Half-Life: Plasma half-life is approximately 3-6 minutes in dogs and cats; in horses, it is similar.
Bioavailability: Bioavailability after subcutaneous or intramuscular injection is high (near 100%).
Protein Binding: Minimal protein binding.

Available Formulations & Strengths

Injectable Solution 1 mg/mL (as hydrochloride) (IV, IM, SC)
Powder for Injection 1 mg vial (reconstitute with sterile water) (IV, IM, SC)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to glucagon or any component
  • Pheochromocytoma (risk of hypertensive crisis)
  • Insulinoma (may stimulate insulin release, causing paradoxical hypoglycemia)
  • Glucagonoma (may exacerbate tumor effects)
Warnings & Clinical Precautions:
  • Use with caution in patients with cardiac disease, as glucagon may increase heart rate and blood pressure.
  • In patients with insulinoma, glucagon may cause a transient increase in blood glucose followed by rebound hypoglycemia due to insulin release.
  • Monitor blood glucose closely during therapy.
  • In neonates, ensure adequate glycogen stores; glucagon may be ineffective in malnourished or premature animals.
  • For GI motility disorders, use only as a diagnostic aid; not a substitute for surgical intervention if needed.
  • Do not use in animals with known hypersensitivity.
  • Use with caution in animals with hepatic disease, as glycogenolysis may be impaired.

Adverse Effects & Reactions

Common:

  • Nausea
  • Vomiting
  • Tachycardia
  • Hypotension or hypertension
  • Injection site reactions

Serious / Severe:

  • Hypoglycemia (rebound, especially in insulinoma)
  • Cardiac arrhythmias
  • Hypertensive crisis (in pheochromocytoma)
  • Anaphylaxis (rare)

Rare:

  • Allergic reactions
  • Hyperglycemia (transient)
  • Electrolyte imbalances

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Beta-blockers (e.g., propranolol) Glucagon may be used to treat beta-blocker overdose; concurrent use may have additive cardiac effects. Moderate
Insulin Glucagon antagonizes the effects of insulin; may cause hyperglycemia if used concurrently. Moderate
Calcium channel blockers (e.g., verapamil) Glucagon may be used to treat overdose; concurrent use may have additive inotropic effects. Moderate
Anticholinergics (e.g., atropine) May enhance the gastrointestinal effects of glucagon. Mild
Warfarin Glucagon may increase the anticoagulant effect of warfarin (unclear mechanism). Mild

Overdose & Toxicity Management

Signs of Toxicity:

  • Nausea
  • Vomiting
  • Diarrhea
  • Tachycardia
  • Hypertension
  • Hypokalemia
  • Hyperglycemia followed by hypoglycemia

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Monitor vital signs and blood glucose. Administer fluids and electrolytes as needed. For severe hypertension, use antihypertensive agents. For hypoglycemia, administer glucose. Discontinue glucagon and provide supportive care.

Food Animal Withdrawal Times

πŸ₯© Meat: 0 daysπŸ₯› Milk: 0 daysπŸ₯š Eggs: 0 days

Glucagon is a naturally occurring hormone with a very short half-life; no withdrawal periods are required for food animals when used according to label. However, extra-label use may require veterinary oversight and adherence to regulatory guidelines.

Storage, Handling & Regulatory Information

Storage Temperature: Store at 2-8Β°C (refrigerate). Do not freeze.

Light Sensitivity: Light-sensitive β€” protect from direct exposure.

Handling & Special Conditions: Protect from light. Reconstituted solutions should be used immediately or stored at 2-8Β°C for up to 24 hours. Discard unused portions.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; approved for human use. Used in veterinary medicine as an extra-label drug.

Extra-Label (Off-Label) Use: In the US, glucagon is not FDA-approved for veterinary use, but it may be used legally under the Animal Medicinal Drug Use Clarification Act (AMDUCA) with a valid veterinarian-client-patient relationship. Extra-label use in food animals requires a withdrawal period established by the veterinarian, but due to its short half-life, a zero withdrawal time is often reasonable.

Clinical Pearls & Practice Notes

πŸ’‘ Clinical Insights: Glucagon is a valuable emergency drug for severe hypoglycemia when IV glucose is not immediately available or when venous access is difficult. It is also used as a diagnostic tool for gastrointestinal motility disorders and as a treatment for beta-blocker or calcium channel blocker overdose. In veterinary patients, it is most commonly used in dogs and cats for insulin overdose or insulinoma. It is important to monitor blood glucose closely after administration, as rebound hypoglycemia can occur, especially in patients with insulinoma. For GI motility, glucagon can help differentiate mechanical obstruction from functional ileus. Always ensure that the patient has adequate glycogen stores; in neonates or malnourished animals, glucagon may be ineffective. Use with caution in patients with cardiac disease or pheochromocytoma. Due to its short half-life, continuous infusion may be necessary for sustained effect. Store properly and protect from light.

References & Literature

  • πŸ“š Plumb's Veterinary Drug Handbook
  • πŸ“š Papich Veterinary Pharmacology and Therapeutics
  • πŸ“š Compendium of Veterinary Products (CVP)