DIGOXIN ( LANOXIN )

GENERIC NAME: digoxin

BRAND NAME: Lanoxin

DRUG CLASS AND MECHANISM: Digoxin is extracted from the leaves of a plant called digitalis lanata. Digoxin increases the strength and vigor of the heart muscle contractions, and is useful in the treatment of heart failure. Digoxin also slows the electrical conduction between the atria and the ventricles of the heart, and is useful in treating abnormally rapid atrial rhythms such as atrial fibrillation, atrial flutter, and atrial tachycardia.

Abnormally rapid atrial rhythms can be caused by heart attacks, excessive thyroid hormones, alcoholism, infections, and many other conditions. During rapid atrial rhythms, electrical signals from the atria cause rapid contractions of the ventricles. Rapid ventricle contractions are inefficient in delivering oxygen and nutrients to the body, causing symptoms of weakness, shortness of breath, dizziness, and even chest pain. Digoxin alleviates these symptoms by blocking the electrical conduction between the atria and ventricles, thus slowing ventricle contractions.

PRESCRIPTION: yes

GENERIC AVAILABLE: yes

PREPARATIONS: tablets (0.125mg, 0.25mg, 0.5mg), capsules (0.05mg, 0.1mg, 0.2mg)

STORAGE: Should be stored in dry, light-resistant, tight container.

PRESCRIBED FOR: Digoxin is used to treat congestive heart failure and the associated symptoms of shortness of breath when lying flat, wheezing, and ankle swelling. Digoxin is also used to slow heart rate in rapid atrial rhythm disturbances such as atrial fibrillation and atrial flutter.

DOSING: Digoxin may be taken with or without food. Digoxin is mainly excreted by the kidneys, and dosages need to be reduced in patients with kidney dysfunction. Digoxin blood levels can be used to monitor dosing and to avoid drug toxicity.

DRUG INTERACTIONS: There is little cushion between a therapeutically beneficial level of digoxin and a toxic level of digoxin. Digoxin toxicity is common, especially in patients with kidney dysfunction. Digoxin toxicity can cause potentially life- threatening heart rhythm disturbances, ranging from very slow to rapid ventricular rhythms. In patients with existing disease of the electrical conduction of the heart, digoxin can precipitate heart block and a seriously slow heart rate.

Patients with low blood potassium levels can develop digoxin toxicity even when digoxin levels are not considered elevated. Similarly, high calcium and low magnesium blood levels can increase digoxin toxicity and produce serious heart rhythm disturbances. Drugs such as quinidine (Quinaglute, Quinidex), verapamil (Calan), and amiodarone (Cordarone) can increase digoxin levels and the risk of toxicity. The co-administration of digoxin and beta blockers, such as propranolol (Inderal Inderal LA), or calcium channel blockers, such as Calan, can cause serious slowing of the heart rate.

When digoxin is taken by patients receiving saquinavir (Fortovase, Invirase) with ritonavir (Norvir), the amount of digoxin in the body can increase by 50%, possibly leading to side effects such as potentially fatal rhythm disturbances, nausea, vomiting, and diarrhea, blurred or yellow vision; headache; weakness; dizziness; apathy; confusion; and mental disturbances such as anxiety, depression, delirium, and hallucinations.

SIDE EFFECTS: The most common side effects are related to digoxin toxicity and heart rhythm disturbances. Other side effects include abdominal pain, nausea, vomiting, loss of appetite, breast enlargement, skin rash, blurred vision, and mental changes.