Glucagon beta-blocker overdose

Positive inotropic and chronotropic, not via activation of (i, receptors, but through glucagon receptors that are G-protein linked to adenylyl cyclase -> basis for its use in beta-blocker overdose. 

A. Severe bradycardia or conduction block resulting in hemodynamically significant hypotension (see p 10). Note After beta-blocker overdose, even exceedingly high doses of isoproterenol may not overcome the pharmacologic blockade of beta receptors, and glucagon (see p 449) is the preferred agent. 

G. Other applications Micromedex notes that glucagon (rDNA origin) may also be used to reduce smooth muscle tone in the gastrointestinal tract. It has also shown to be effective in the treatment of anaphylaxis, biliary tract pain, beta-adrenergic blocker overdose, esophageal obstruction, and as premedication in endoscopic procedures. 

Glucagon has also been used to stimulate insulin and C-peptide secretion, to see whether the islets still produce insulin, as a stimulatory test during pheochromocytoma, hyperinsulinism, and Zollinger-Ellison syndrome, or as an additive in upper gastrointestinal X-ray investigations (0.5-1 mg). It has been used in myocardial infarction, although its inotropic effects may present a risk. It has also been used to treat overdoses with beta-blockers (3) and calcium channel blockers (4), although its efficacy in such cases has only been demonstrated in animals (5) and to treat overdose with tricyclic antidepressants (6,7). 

Bailey B. Glucagon in beta-blocker and calcium channel blocker overdoses a systematic review. J Toxicol Clin Toxicol 2003 41(5) 595-602. 

II. Indications. Inamrinone may be useful as a third-line inotropic agent for patients with beta-blocker, mixed beta- and alpha-blocker (eg, labetalol), or calcium antagonist overdose, when Intravenous fluids, atropine, beta agonists, and glucagon have failed to restore cardiac output and blood pressure. 

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