Digitalis Toxicity

Definition

Digitalis toxicity refers to the adverse effects that can occur when the cardiac glycoside drug digitalis, commonly known as digoxin, is present in the body at toxic levels. This can happen with either accidental or intentional overdose, and it can have serious consequences on the heart's electrical activity and function.

5 Must Know Facts For Your Next Test

1. Digitalis toxicity can occur with both therapeutic and supratherapeutic doses of digoxin, and is more likely in patients with impaired renal function.
2. The most common symptoms of digitalis toxicity include nausea, vomiting, diarrhea, abdominal pain, and visual disturbances like yellow-green halos around lights.
3. Cardiac manifestations of digitalis toxicity include bradycardia, heart block, ventricular tachyarrhythmias, and life-threatening dysrhythmias.
4. Management of digitalis toxicity involves immediate cessation of the drug, supportive care, and potential use of digoxin-specific antibody fragments to bind and neutralize the excess digitalis.
5. Preventive measures for digitalis toxicity include careful dosing, monitoring of serum digoxin levels, and consideration of patient factors like age, renal function, and electrolyte status.

Review Questions

• Explain the mechanism by which digitalis drugs can lead to cardiac toxicity.
  • Digitalis drugs, such as digoxin, work by inhibiting the sodium-potassium ATPase pump in cardiac myocytes. This leads to an increase in intracellular sodium, which then drives the sodium-calcium exchanger to increase intracellular calcium levels. The elevated calcium enhances myocardial contractility, but can also predispose the heart to abnormal electrical activity and arrhythmias, particularly when digitalis levels become toxic.
• Describe the clinical presentation and risk factors associated with digitalis toxicity.
  • The clinical presentation of digitalis toxicity includes both gastrointestinal symptoms, such as nausea, vomiting, and abdominal pain, as well as cardiac manifestations like bradycardia, heart block, and ventricular tachyarrhythmias. Patients with impaired renal function are at higher risk for developing digitalis toxicity, as the drug is primarily cleared by the kidneys. Other risk factors include advanced age, electrolyte imbalances, and concomitant use of certain medications that can interact with digoxin.
• Discuss the management strategies for patients experiencing digitalis toxicity, including the role of digoxin-specific antibody fragments.
  • The immediate management of digitalis toxicity involves discontinuation of the drug and supportive care. In severe cases, digoxin-specific antibody fragments (Fab) may be administered to rapidly bind and neutralize the excess digitalis in the body. These antibody fragments work by forming a tight complex with digitalis, preventing its interaction with the sodium-potassium ATPase pump and effectively reversing the toxic effects. Other supportive measures may include fluid and electrolyte management, as well as antiarrhythmic medications to control any life-threatening cardiac dysrhythmias.

Related terms

Cardiac Glycosides: A class of drugs that act on the heart by inhibiting the sodium-potassium ATPase pump, leading to increased intracellular calcium and enhanced myocardial contractility.

Digoxin: The most commonly used cardiac glycoside, prescribed for the management of heart failure and certain types of arrhythmias.

Arrhythmias: Abnormal heart rhythms that can be caused by digitalis toxicity, including bradycardia, heart block, and ventricular tachyarrhythmias.