Glucagon Injectable: Uses, Mechanism, Dosage, Side Effects, Precautions, and Clinical Applications
Introduction
Glucagon injectable is a life-saving hormone therapy delivered via subcutaneous, intramuscular, or intravenous injection. It is primarily used as an emergency remedy for severe hypoglycemia in patients with diabetes who are unable to take oral glucose, and as a diagnostic aid in radiologic procedures to temporarily relax the gastrointestinal tract. Beyond its approved uses, glucagon has several important off-label applications in emergency and diagnostic medicine. This article provides a detailed exploration of glucagon’s pharmacology, clinical utility, administration guidelines, risk profile, and practical considerations, tailored for both healthcare professionals and informed readers in the US and Europe.
1. Clinical Uses & Applications
A. Approved (On-Label) Uses
- Emergency Treatment of Severe Hypoglycemia
Glucagon is indicated for treating life-threatening low blood sugar in both adults and children with diabetes who cannot intake oral carbohydrates or are unconscious Drugs.comMedlinePlusFDA Access Data. - Diagnostic Aid in Radiologic Examinations
It is used to relax smooth muscles of the stomach, duodenum, and colon, facilitating imaging studies such as barium studies or ERCP Drugs.comFDA Access Data+1Mayo Clinic.
B. Off-Label and Emerging Uses
- Beta-blocker and Calcium Channel Blocker Overdose
High-dose glucagon can reverse bradycardia and hypotension in refractory overdoses by increasing cyclic AMP in cardiac tissue NCBI. - Esophageal Food Impaction
Its ability to relax esophageal smooth muscle makes it useful in some cases of food bolus obstruction, though efficacy may vary WikipediaNCBI. - Refractory Anaphylaxis
Emerging evidence supports its use in anaphylaxis unresponsive to epinephrine, especially in cases complicated by beta-blocker use NCBI.
2. Mechanism of Action
Glucagon is a 29-amino acid peptide hormone that activates hepatic glucagon receptors (G protein-coupled receptors) → stimulates adenylate cyclase → increases cAMP → activates protein kinase A → stimulates glycogenolysis → increases blood glucose levels. Additionally, glucagon induces smooth muscle relaxation in the gastrointestinal tract by similar cAMP-mediated mechanisms WikipediaNCBIDrugBank.
3. Dosage & Administration
A. Severe Hypoglycemia
- Routes: Subcutaneous (SC), Intramuscular (IM), or Intravenous (IV, under medical supervision) Drugs.comFDA Access DataMedlinePlus.
- Typical Dose: 1 mg for adults—administer promptly at first sign of severe hypoglycemia FDA Access DataDrugs.comMedlinePlus.
- Post-Injection: Call emergency services; once the patient awakens and can swallow, provide fast and long-acting carbohydrates FDA Access DataMedlinePlus.
- Repeat Assessment: If no response within ~15 minutes, a second dose may be administered as needed, while awaiting medical care FDA Access DataMedlinePlus.
B. Diagnostic Aid (Radiology)
- Dose: Same 1 mg dose reconstituted from powder; timing determined by procedure duration FDA Access Data+1Mayo Clinic.
- Administration: Given just before imaging begins to reduce GI motility and improve visualization FDA Access Data+1.
C. Off-Label Uses
- Overdose Treatment: High-dose IV glucagon may be used; dosing protocols vary and entail careful monitoring.
- Esophageal Impaction: Typically 1 mg IM or IV; efficacy is inconsistent.
4. Side Effects and Adverse Reactions
From clinical studies and postmarketing data, glucagon is generally well tolerated but may cause:
- Common: Nausea, vomiting, headache; injection site swelling or erythema; dizziness; decreased blood pressure; asthenia; somnolence; pallor; diarrhea FDA Access Data+1PMC.
- Less Common but Clinically Important: Tachycardia, hypertension, hypersensitivity reactions, potential for hypoglycemia in patients with insulinoma or glucagonoma, necrolytic migratory erythema with high-dose infusions FDA Access Data+3FDA Access Data+3FDA Access Data+3NCBI.
5. Precautions and Contraindications
- Contraindications:
- Pheochromocytoma: Risk of catecholamine surge → hypertensive crisis FDA Access Data+1.
- Insulinoma or Glucagonoma: Risk of paradoxical hypoglycemia or exacerbating glucagonoma symptoms FDA Access Data+2FDA Access Data+2.
- Known hypersensitivity to glucagon or excipients FDA Access Data+1.
- Warnings:
- Decreased hepatic glycogen (e.g., malnutrition, alcoholism) may reduce efficacy.
- Use caution in patients with coronary artery disease due to potential tachycardia or elevated BP FDA Access Data+1.
6. Clinical Applications & Practical Considerations
Emergency Kits and Self-Administration
- Many diabetic patients keep glucagon emergency kits at home, with training for caregivers on reconstitution and administration MedlinePlusFDA Access Data+1.
Monitoring and Aftercare
- After administration, monitor airway and glucose response. Supportive care includes positioning to prevent aspiration, neurologic observation, and refeeding when safe.
In Hospital Settings
- IV glucagon may be preferred for rapid onset; providers should monitor cardiovascular parameters and glucose closely.
- For overdose cases (beta-blocker or calcium-channel blocker), glucagon may be used with supportive therapies (fluids, vasopressors).
Radiologic Use
- Ensure patients are fasted and recollect oral intake after study to replenish hepatic glycogen FDA Access Data+1.
7. Summary Table
| Section | Key Highlights |
|---|---|
| Uses | Severe hypoglycemia; GI relaxation for imaging; off-label: overdose, impaction |
| Mechanism | Raises blood glucose via cAMP → glycogenolysis; relaxes GI smooth muscle |
| Dosage | 1 mg SC/IM/IV; repeat if no response; specific protocols vary with indication |
| Side Effects | Nausea, vomiting, headache, injection site reactions, tachycardia, hypertension |
| Precautions | Avoid in pheochromocytoma, insulinoma, glucagonoma, glycogen depletion |
| Clinical Use | Emergency kits, hospital IV administration, radiology, overdose management |
References
- FDA Prescribing Information for Glucagon for Injection – Indications, dosage, contraindications, adverse effects, pharmacodynamics.
- MedlinePlus Drug Information: Glucagon Injection – Use in hypoglycemia, administration tips, onset of action.
- StatPearls / NCBI Bookshelf: Clinical Applications and Off-Label Use of Glucagon – Mechanism and off-label uses including overdose and food impaction.
