Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: digoxin

BRAND NAME: Lanoxin

DRUG CLASS AND MECHANISM: Digoxin increases the strength and vigor of heart contractions, and is useful in the treatment of heart failure. It is extracted from the leaves of a plant called digitalis lanata. Digoxin increases the force of contraction of the muscle of the heart by inhibiting the activity of an enzyme (ATPase) that controls movement of calcium, sodium and potassium into heart muscle. Calcium controls the force of contraction. Inhibiting ATPase increases calcium in heart muscle and therefore increases the force of heart contractions. Digoxin also slows 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 ventricular contractions are inefficient in pumping blood containing 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 ventricular contractions. The FDA approved digoxin in 1975.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Tablets: 0.125, and 0.25 mg; Elixir: 0.05, 0.25, and 0.1 mg/ml.

STORAGE: Digoxin should be stored at room temperature, 59-86 F (15-30 C) and protected from light.

PRESCRIBED FOR: Digoxin is used for mild to moderate congestive heart failure and for treating an abnormal heart rhythm called atrial fibrillation.

DOSING: Digoxin may be taken with or without food. Digoxin is primarily eliminated by the kidneys; therefore, the dose of digoxin should be reduced in patients with kidney dysfunction. Digoxin blood levels are used for adjusting doses in order to avoid toxicity. The usual starting dose is 0.0625-0.25 mg daily depending on age and kidney function. The dose may be increased every two weeks to achieve the desired response.

DRUG INTERACTIONS: Drugs such as verapamil (Calan, Verelan, Verelan PM, Isoptin, Isoptin SR, Covera-HS), quinidine (Quinaglute, Quinide), amiodarone (Cordarone), indomethacin (Indocin, Indocin-SR), alprazolam (Xanax, Xanax XR, Niravam), spironolactone (Aldactone), and itraconazole (Sporanox) can increase digoxin levels and the risk of toxicity. The co-administration of digoxin and beta-blockers [for example propranolol (Inderal, Inderal LA) or calcium channel blockers (for example, verapamil), which also reduces heart rate, can cause serious slowing of the heart rate.

Diuretic-induced [for example, by furosemide (Lasix)] reduction in blood potassium or magnesium levels may predispose patients to digoxin-induced abnormal heart rhythms.

Saquinavir (Invirase) and ritonavir (Norvir) increase the amount of digoxin in the body and may cause digoxin toxicity.

PREGNANCY: There are no adequate studies in pregnant women.

NURSING MOTHERS: Digoxin in secreted in breast milk at concentrations similar to concentrations in the mothers blood. However, the total amount of digoxin that will be absorbed from breast milk by the infant may not be enough to cause effects. Caution should be exercised by nursing mothers who are taking digoxin.

SIDE EFFECTS: Common side effects include nausea, vomiting, headache, dizziness, skin rash, and mental changes. Many digoxin side effects are dose dependent and happen when blood levels are over the narrow therapeutic range. Therefore, digoxin side effects can be avoided by keeping blood levels within the therapeutic level. Serious side effects associated with digoxin include heart block, rapid heartbeat, and slow heart rate. Digoxin has also been associated with visual disturbance (blurred or yellow vision), abdominal pain, and breast enlargement. 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 disturbances in heart rhythm.

Suggested Reading by Our Doctors

• Congestive Heart Failure - Read about congestive heart failure symptoms like fatigue, abdomen, leg and ankle swelling, shortness of breath, sleeplessness, increased urination, nausea, abdominal pain, and decreased appetite.
• Heart Attack - Overview on heart attack (myocardial infarction) and heart attack symptoms including jaw pain, headache, shortness of breath, nausea, vomiting, heartburn, sweating, and more.
• Atrial Fibrillation - Learn about atrial fibrillation including what it is, what happens during atrial fibrillation, symptoms, risk factors, how it is diagnosed, and how it is treated

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