Beta blockers overdose

Early echocardiographic evaluation is important in beta-blocker overdose and can prevent delay in the diagnosis and treatment of cardiac toxicity. 

Love JN, Howell JM, Litovitz TL, Klein-Schwartz W. Acute beta blocker overdose factors associated with the development of cardiovascular morbidity. J Toxicol Clin Toxicol 2000 38(3) 275-81. 

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. 

Hormone from pancreatic A cells. Increases blood sugar via increased cAMP. Used in hypoglycemia and as an antidote 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. 

Quinidine overdose should be treated with symptomatic and supportive therapy. Quinidine should be used with caution when coadministering with calcium channel blockers, diuretics, beta-blockers, antibacterials, antifungals, and antiarrhythmics.97... 

Treatment for verapamil overdose includes gastric lavage, administration of activated charcoal, symptomatic and supportive cardiovascular treatment, and calcium gluconate injection. Verapamil should be used carefully with calcium salts, beta-blockers, antineoplastics, antiepileptics, antibacterials, anxiolytics, and anti-arrhythmics. 

E. Toxicity The common adverse effects include gastrointestinal distress, tremor, and insomnia. Severe nausea and vomiting, hypotension, cardiac arrhythmias, and convulsions may result from overdosage. Very large overdoses (eg, in suicide attempts) are potentially lethal because of the arrhythmias and convulsions. Beta-blockers are useful antidotes for severe cardiovascular toxicity from theophylline. 

B. Toxicodynamics Toxicodynamics is a term used to denote the injurious effects of toxins, ie, their pharmacodynamics. A knowledge of toxicodynamics can be useful in the diagnosis and management of poisoning. For example, hypertension and tachycardia are typically seen in overdoses with amphetamines, cocaine, and antimuscarinic drugs. Hypotension with bradycardia occurs with overdoses of calcium channel blockers, beta-blockers, and sedative-hypnotics. Hypotension with tachycardia occurs with tricyclic antidepressants, phenothiazines, and theophylline. Hyperthermia is most frequently a result of overdose of drugs with antimuscarinic actions, the salicylates, or sympathomimetics. Hypothermia is more likely to occur with toxic doses of ethanol and other CNS depressants. Increased respiratory rate is often a feature of... 

The most likely drug to be needed in an overdose due to this substance is an anticonvulsant, but beta-blockers are appropriate when cardiac arrhythmias are present... 

The most dangerous toxic effect of theophylline is convulsions. The cardiovascular toxicity of theophylline (eg, arrhythmia.s) often responds to beta-blockers. The answer is (L). Hepatotoxicity due to overdose of acetaminophen (more likely in alcoholic patients) is due to the formation of a toxic metabolite. Early administration of acetylcysteine can be protective. The answer is (A). 

A. Check blood pressure and pulse rate and rhythm. Perform cardiopulmonary resuscitation (CPR) if there is no pulse and perform advanced cardiac life support (ACLS) for arrhythmias and shock. Note that some ACLS drugs may be ineffective or dangerous in patients with dmg- or poison-induced cardiac disorders. For example, procainamide is contraindicated in patients with tricyclic antidepressant overdose, and atropine and isoproterenol are ineffective in patients with beta-blocker poisoning. 

B. Epinephrine is occasionally used for hypotension resulting from overdose by beta blockers, calcium antagonists, and other cardiac-depressant dmgs. 

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. 

---