DIGITALIS OVERDOSE

Digitalis is a drug commonly used in patients having congestive heart failure and atrial fibrillation. The drug is derived from oleander, foxglove, and lily of the valley plants. Digoxin is the most commonly used digitalis preparation. It acts by increasing heart muscle contraction in patients with congestive heart failure and slows down the heart rate in patients who have atrial fibrillation with a fast heartbeat. Other indications for the use of digoxin include rhythm disturbances called atrial flutter and supraventricular tachycardia.

It is important to know that digoxin is metabolized in the liver but excreted (removed from the body) by the kidney. Therefore, people who have poor kidney function and who use the drug run the risk of digoxin overdose. It is estimated that nearly 0.5% of all hospital admissions are related to digoxin toxicity; the elderly (those older than 70 years) carry the highest risk. Predisposing factors leading to digoxin overdose include patients with chronic illness such as emphysema and liver failure, metabolic problems such as elevated blood calcium or potassium levels, and drug interactions with quinidine, calcium channel blockers, and water pills (hydrochlorothiazide, furosemide, amiloride, and spironolactone).

Digoxin overdose is detected by the clinical symptoms mentioned below along with specific electrocardiographic (ECG) findings. Digoxin overdose, if detected, is curable.

Patients with digoxin overdose can have a variety of symptoms including nausea, vomiting, yellow-green color vision disturbance, confusion, numbness, weakness, fatigue, shortness of breath, dizziness, and headaches. The physical examination may not be helpful in diagnosing digoxin toxicity. Blood tests may give helpful clues toward making the diagnosis, specifically the digoxin blood level, kidney blood test, and calcium and magnesium levels.

Digoxin overdose can be fatal, leading to life-threatening arrhythmias (abnormal heart rhythms) called ventricular tachycardia. The diagnosis must be suspected so that appropriate therapy can be administered.

The basic treatment for any overdose includes supportive care (making sure there is a blood pressure and a pulse). Thereafter, your physician will focus on specific treatment of major rhythm problems and correcting any underlying metabolic abnormalities such as low potassium or low magnesium levels. If the diagnosis is suspected, your physician may try to prevent further absorption from the stomach by making you drink activated charcoal. In some situations the physician may have to place a tube into the stomach to wash out the excess drug. This is called gastric lavage.

In certain critical situations the physician may recommend a specific antidote called digoxin-immune FAB (Digibind). Digibind removes digoxin from the tissues and significantly improves life-threatening rhythm disturbances. Digibind is recommended when life-threatening rhythm disturbances are occurring, when there is significant slowing of the heart caused by digoxin, and when the digoxin or the potassium level is very high. Some patients may be allergic to Digibind, but overall the complication rate from Digibind is low.

• Remember, there are two types of digitalis overdose scenarios: the acute digitalis overdose occurring in a patient who accidentally or intentionally takes too much digoxin and the chronic digitalis overdose occurring in the patient with impaired kidney function who cannot adequately excrete the drug.
• Read all of the labels on the bottles and take the medication as prescribed.

• Don't become dehydrated, as this is another precipitating factor leading to digoxin overdose.
• Don't forget that, as we get older, we lose some kidney function and therefore doses of digoxin must be adjusted.
• Don't forget the possibility of drug interactions with digoxin, and discuss this with your physician whenever starting a new medication.

• If you are taking digoxin and feel nauseated.
• If you feel an irregular heartbeat or palpitations.
• If someone you know is on digoxin and becomes confused, disoriented, agitated, or starts to hallucinate.

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