Glucagon in bradycardia

Q: Intravenous (IV) glucagon should be administered in suspected cases of?- select one

A) beta blocker (BB) overdose

B) calcium channel blocker (CCB) overdose 

C) both BB and CCB overdoses

Answer: C

Both BB and CCM overdoses require IV glucagon with a bolus dose of 3 to 10 mg over five minutes, and if the condition persists, with a continuous infusion dose of 3 to 5 mg per hour. This can be titrated by monitoring the blood pressure (BP) response, more than the heart rate (HR) response, with an ultimate objective of sustained hemodynamics. Some experts argue that glucagon only helps in increasing the HR but not the BP, so other modalities, which should be tried first, such as atropine (in acute situations), IV calcium, or a temporary pacemaker. Glucagon should be used either as an adjuvant or a second line of treatment.

Glucagon activates adenylate cyclase, causing an increase in adenosine 3'-5'-cyclic monophosphate (cAMP). Elevations in cAMP increase the intracellular pool of calcium available for release during depolarization, augmenting contractility.

Two major caveats of using Glucagon are severe vomiting, which may require simultaneous administration of an anti-emetic like ondansetron. The second caveat is tachyphylaxis with IV infusion.

#toxicology

#pharmacology

#cardiology

References:

1. Kusumoto FM, Schoenfeld MH, Barrett C, et al. 2018 ACC/AHA/HRS Guideline on the Evaluation and Management of Patients With Bradycardia and Cardiac Conduction Delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2019; 74:e51.

2. Bailey B. Glucagon in beta-blocker and calcium channel blocker overdoses: a systematic review. J Toxicol Clin Toxicol 2003; 41:595.

3. Mahr NC, Valdes A, Lamas G. Use of glucagon for acute intravenous diltiazem toxicity. Am J Cardiol 1997; 79:1570.

4. Senart AM, LeClair LA. Cardiovascular and Adverse Effects of Glucagon for the Management of Suspected Beta Blocker Toxicity: a Case Series. J Med Toxicol 2023; 19:9.