Cardiac Glycoside Plant Poisoning Medication

Categories of drugs used to manage cardiac glycoside plant toxicity include the following:

• Drugs to minimize absorption and increase excretion

• Drugs that lower extracellular potassium

• Antidysrhythmics

• Antidotes (eg, digoxin Fab fragments)

Hyperkalemia usually results from acute overdose and represents redistribution of potassium from intracellular to extracellular compartment; therefore, drugs of choice include agents that promote potassium redistribution from extracellular to intracellular compartments. Avoid calcium, as it may exacerbate effects of cardiac glycosides and may promote rhythm deterioration when used in this context.

Class Summary

Activated charcoal adsorbs ingested medication remaining in the gastrointestinal tract and creates a concentration gradient to "pull back" medication circulating in the bloodstream. It is most effective if administered within 1 hour of ingestion. In selected cases, repeated doses may be beneficial if the toxin is entero-hepatically metabolized, allowing a second opportunity to bind it and remove it from the body.

Digoxin immune FAB is a specific antidote that may be effective in some forms of cardiac glycoside plant poisoning. This agent has been used successfully in patients with oleander toxicity and may cross-react with other cardiac glycosides.

Activated charcoal (Actidose-Aqua, Actidose/Sorbitol EZ-Char, Kerr Insta-Char)

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Activated charcoal is used in emergency treatment for poisoning caused by drugs and chemicals. A network of pores adsorbs 100-1000 mg of drug per gram of activated charcoal. Activated charcoal does not dissolve in water.

Administer activated charcoal as soon as possible after poison ingestion. Repeated doses may help to lower systemic levels of ingested compounds. The first dose may be given with a cathartic (eg, sorbitol); subsequent doses should be given without a cathartic, as often as q2-6h, and should not be given in presence of ileus.

Digoxin immune FAB (DigiFab)

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This agent consists of sheep-derived IgG antibodies to digoxin. It may be helpful in certain situations, including hyperkalemia not quickly responsive to standard treatments, life-threatening dysrhythmias, and cardiac arrest.

Because serum digoxin/digitoxin levels do not reflect ingested amount of plant cardiac glycoside, drug levels should not be used to calculate Fab dose in these cases. Elevated serum levels of digoxin or digitoxin only confirm exposure. An undetectable level of serum cardiac glycosides does not rule out exposure. Elevated serum potassium should be a useful indicator when considering this agent.

Class Summary

Intravenous administration of regular insulin along with glucose (in the form of 50% dextrose in water [D50W]) redistributes potassium intracellularly. Onset of action is 30 min and duration of action is 4-6h.

This regimen is used for life-threatening hyperkalemia (>5.5 mEq/L). It should be used cautiously with digoxin Fab as profound hypokalemia may occur. The serum glucose level should be monitored and additional D50W administered if needed.

Insulin regular human (Humulin R, Novolin R)

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The adult dose of glucose plus insulin is 50 g glucose plus 20 U regular insulin IV over 1 hour. The pediatric dose is 0.5-1 g glucose/kg; 1 U regular insulin IV is given for every 3 g of total glucose.

Class Summary

Alkalosis created by bicarbonate leads to a redistribution of potassium intracellularly. Onset of action is 5-10 min and duration of action is 1-2 h. This agent is used for life-threatening hyperkalemia (>5.5 mEq/L). Use cautiously with digoxin Fab as profound hypokalemia may occur.

Sodium Bicarbonate (Neut)

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Intravenous sodium bicarbonate, followed by continuous infusion used for its alkalization properties to maintain a serum pH of 7.5-7.55, has reversed hypotension and resulted in narrowing of the QRS complex in isolated case reports.

Class Summary

Used to treat variety of bradydysrhythmias and tachydysrhythmias occurring with cardiac glycoside toxicity.

Atropine IV/IM (AtroPen)

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Atropine is used for bradycardia and conduction blocks in standard Acute Cardiac Life Support (ACLS) doses: 0.5-1 mg or 0.04 mg/kg IV every 5 min, no more than 3 mg. Doses < 0.1 mg in children or 0.5 mg in adults may lead to paradoxical bradycardia.

Class Summary

Phenytoin may reverse digitalis-induced prolongation of the action potential in myocardial cells and may suppress digitalis-induced tachydysrhythmia.

Phenytoin (Dilantin, Phenytek)

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Phenytoin prolongs effective refractory period and depresses spontaneous depolarization in ventricular tissues. Phenytoin is useful for ventricular dysrhythmias, such as ventricular fibrillation, ventricular tachycardia, and premature ventricular contractions. It is the drug of choice for cardiac glycoside–induced tachydysrhythmia following digoxin FAB fragments. This agent is the only antidysrhythmic that stabilizes myocardium and improves conduction through the atrioventricular (AV) node. Monitor serum phenytoin levels closely to ensure therapeutic levels of 10-20 mcg/mL.

Class Summary

These agents are used to treat a variety of bradydysrhythmia and tachydysrhythmia occurring with cardiac glycoside toxicity.

Lidocaine (Xylocaine)

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Lidocaine is a class IB antiarrhythmic that increases the electrical stimulation threshold of the ventricle, suppressing automaticity of conduction through the tissue.

Class Summary

Magnesium is useful as a temporizing antiarrhythmic agent until digoxin Fab fragments are available. It may be a lifesaving adjunct in the treatment of digoxin-induced ventricular tachycardia or ventricular fibrillation.

Magnesium sulfate (MgSO4)

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Magnesium sulfate possesses antidysrhythmic properties that are beneficial in treatment of digoxin toxicity. Its mechanism is not entirely understood but may suppress delayed afterdepolarizations, reactivate the Na+-K+-ATPase pump, and block the action of the cardiac glycosides at the sarcolemma Na+-K+-ATPase pump.

Magnesium is a cofactor in enzyme systems involved in neurochemical transmission and muscular excitability. Although serum magnesium levels may be normal, existence of intracellular hypomagnesemia has been hypothesized; therefore, magnesium may be beneficial.

For torsade de pointes, ACLS protocol for patients with a pulse calls for 1-2 g (diluted in 50-100 mL 5% D5W) given by slow IV infusion over 5-60 minutes, then 0.5-1 g/hr IV. For cardiac arrest, the dosage is 1-2 g (diluted in 10 mL D5W) infused over 5-20 minutes.