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Digoxin

Digoxin

Brand Names

Lanoxin

Overview

Digoxin was once a very widely prescribed heart medication used to treat congestive heart failure and irregular heart rhythms, particularly atrial fibrillation, but it has become increasingly controversial. Research in Taiwan suggests that digoxin might increase the risk of stroke and premature death instead of preventing these disasters in people with atrial fibrillation (Canadian Journal of Cardiology, Oct. 2014).

Digoxin is a digitalis heart medicine that to this day is derived from the leaves of a plant related to foxglove. Digitalis has been used medically for over 200 years.

People with heart failure often experience fluid retention, sensitivity to cold, fatigue and difficulty breathing after mild exercise, and a nighttime cough, especially when they lie down.

Digoxin works partly by increasing the pumping power of the heart. It can also help slow an abnormal heart when atrial rhythms gets out of control. But the medication can be complex to manage, especially in older people or in infants.

This medication requires careful monitoring to prevent an overdose as the therapeutic level is very close to the toxic dose. Periodic blood tests are crucial.

Side Effects

Signs of digitalis toxicity include loss of appetite, nausea, diarrhea, vomiting, stomach pain, blurred or disturbed color vision, headache, drowsiness, fatigue, and muscle weakness.

If any of these symptoms occur, contact your physician immediately.

Other adverse reactions may include personality change, depression, confusion, disorientation, apathy, bad dreams and hallucinations. Any side effects should be brought to a doctor’s attention promptly. Heart rhythm changes are potentially serious reactions to the medication.

Interactions

Digoxin can interact with a wide range of over-the-counter and prescription medications. Certain drugs interact so badly that they should not usually be given to someone taking digoxin. They include the gout medicine colchicine, the strong anti-nausea drug dolasetron (Anzemet), the anti-arrhythmic drug dronedarone (Multaq) and the multiple sclerosis medicine fingolimod (Gilenya). Milnacipran (Savella), used to treat fibromyalgia, can increase the risk of dizziness and fainting and irregular heart rhythms in conjunction with digoxin. The antibiotics neomycin and paromomycin can lower digoxin levels unacceptably.

Other interactions can also be troublesome and should be discussed with the physician.

Antacids, for example, may diminish the proper absorption of digoxin. So can certain diarrhea medicines.

A number of other medications, such as amiodarone (Cordarone), propafenone (Rythmol) and quinidine drugs, may make Lanoxin more toxic.

So can Sandimmune, used to prevent transplant rejection.

Calcium-blocking blood pressure medicines like nifedipine (Procardia), diltiazem (Cardizem CD) or verapamil (Calan SR) may also increase digoxin levels.

Diuretics such as furosemide Lasix are often prescribed in conjunction with Lanoxin. A patient taking both medicines must be monitored carefully, however, as the diuretic may make the body lose too much potassium or magnesium. This could lead to serious changes in heart rhythm.

One of the trickiest interactions is that of Lanoxin with erythromycin and tetracycline. For reasons that are not well understood, about one person in ten harbors bacteria in the gut that metabolizes digoxin. If this intestinal flora is wiped out with an antibiotic, the person may suddenly be exposed to much more Lanoxin than usual, even though they may still be swallowing the exact same dose.

Because of these possible complications, never add any other prescription or over-the-counter medications to Lanoxin without first checking with your pharmacist and physician.

Herbal Interactions

Extracts of the herb hawthorn may increase the activity (but not necessarily the toxicity) of cardiac tonics such as digitalis. Hawthorn is not recommended for people who are taking digoxin.

Licorice can greatly increase potassium loss when taking medicines such as Lanoxin; severe potassium loss greatly increases the risk of heart rhythm irregularities in people taking Lanoxin.

The herb cascara_sagrada taken with Lanoxin also could result in excessive potassium loss with resulting heart rhythm irregularities.

The herb St. John’s wort can speed elimination of digoxin from the body, which could reduce its effectiveness.

Psyllium can affect the absorption of Lanoxin; if you take it, it is best to do so at least an hour after taking Lanoxin.

Never stop taking Lanoxin or switch to another brand of digoxin unless your physician is monitoring closely. Because the effective dose is so close to the toxic dose, this could be dangerous.

Special Precautions

People with reduced kidney function generally require lower doses of digoxin. As people age, their kidneys may no longer process this medicine as efficiently. This is another reason why periodic blood tests for digoxin levels are essential.

It is also crucial to monitor both potassium and magnesium levels. If these essential minerals become depleted because of diuretic therapy, digoxin can become extremely dangerous. Blood tests are the only way to determine electrolyte levels.

Taking the Medicine

It is usually recommended that digoxin be taken at the same time and in the same way each day.

For many people the most convenient time is with breakfast. However, food high in fiber such as oat bran or bran muffins may reduce the absorption of this drug. If your breakfast tends to be high in fiber, you might want to schedule your Lanoxin for another time of day.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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