Digoxin toxicity compared with myocardial digoxin and potassium concentration.

Area of Science:

• Cardiovascular Pharmacology
• Veterinary Medicine
• Clinical Toxicology

Background:

• Digoxin is a cardiac glycoside used to treat heart failure and arrhythmias.
• Electrolyte imbalances, particularly hypokalemia, can increase digoxin toxicity.
• The effects of concomitant diuretic or mineralocorticoid administration on digoxin pharmacodynamics and toxicity are not fully elucidated.

Purpose of the Study:

• To investigate the impact of diuretics and mineralocorticoids on myocardial digoxin and potassium concentrations.
• To evaluate the relationship between these concentrations and the occurrence of ventricular arrhythmias in dogs.

Main Methods:

• Twenty-nine dogs were administered oral digoxin for eight days.
• Dogs were divided into groups receiving either diuretics or a mineralocorticoid alongside digoxin.
• Following intravenous digoxin challenge, plasma and cardiac muscle samples were analyzed for digoxin and potassium levels, and arrhythmias were monitored.

Main Results:

• Myocardial potassium decreased in digoxin-treated dogs but increased in those receiving diuretics or mineralocorticoids.
• Ventricular arrhythmias occurred in hypokalemic dogs, mineralocorticoid-treated dogs, and those receiving a toxic digoxin dose.
• Myocardial digoxin concentrations were higher in hypokalemic and high-dose digoxin groups, but no clear correlation was found between arrhythmias and myocardial digoxin or potassium levels.

Conclusions:

• Concomitant administration of diuretics or mineralocorticoids alters myocardial potassium balance during digoxin therapy.
• Hypokalemia and high-dose digoxin increase the risk of arrhythmias, independent of myocardial digoxin concentration.
• Further research is needed to clarify the complex interactions between digoxin, electrolytes, and arrhythmogenesis.