8 Digoxin Interactions You Should Know About

Digoxin (Lanoxin) has been used to treat heart problems since it was first approved in the mid-1950s. Even though it has been around for a long time, it’s now being used less often. But why? 

Digoxin can cause serious side effects, even at typical doses. And it can interact with a number of medications, too. 

Even so, your healthcare provider may decide digoxin is the best option for you. Regular blood monitoring helps ensure you’re taking the right dosage. And managing drug interactions is one way to prevent side effects from becoming worse.

Digoxin interactions to know about

Digoxin is a narrow therapeutic index medication. This means the level of medication in your blood must remain within a small window. In other words, a small change in your digoxin levels can make a big difference in how well it works. 

Higher digoxin levels can mean more side effects, including digoxin toxicity. And lower levels can prevent it from working as well. Regular monitoring is done to ensure you stay in a safe range.

Because of this, it’s important to know about interactions that can affect your digoxin levels. Below, we list several interactions that are common or more serious. Share your current medication list with your healthcare provider and pharmacist. They can identify any others that may affect you.

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1. Certain antibiotics

Antibiotics are medications that help treat or prevent bacterial infections. But mixing digoxin with certain antibiotics can cause your digoxin levels to get too high. In some cases, blood levels can be 100% higher than normal.

Some examples of these antibiotics include: 

• Clarithromycin

• Erythromycin (Ery-Tab)

• Tetracycline 

• Sulfamethoxazole/trimethoprim (Bactrim DS)

Another common antibiotic that might interact with digoxin is azithromycin (Zithromax). It’s often referred to as a “Z-Pak.” Azithromycin can increase digoxin levels, but it’s unclear by how much. Make sure your healthcare provider knows you’re taking digoxin before starting any antibiotic. 

Nausea, vomiting, and diarrhea are common antibiotic side effects. But they’re also common signs of digoxin toxicity. Let your healthcare provider know right away if these develop during treatment.

2. Heart rhythm medications

Heart rhythm medications (antiarrhythmics) can also interact with digoxin. You might be taking one of these if you have a heart rhythm condition, like atrial fibrillation. 

The following heart rhythm medications can increase digoxin levels by more than 50%:

• Propafenone

• Dronedarone (Multaq)

• Quinidine

• Amiodarone (Pacerone)

Dronedarone and other medications that affect heart rate, like sotalol (Betapace) and dofetilide (Tikosyn), can also interact in other ways. When combined with digoxin, they can cause new or worsening heart rhythm problems. 

3. Calcium channel blockers

Calcium channel blockers are a group of medications mostly used to treat high blood pressure. Some can also be used for chest pain and heart rhythm problems. Common examples include diltiazem (Cardizem, Cartia XT), verapamil, and nifedipine (Procardia, Procardia XL).

All three of these medications can increase the amount of digoxin in your blood. And both diltiazem and verapamil can slow down your heart rate, too. Your heart rate may slow down too much (called bradycardia) when they’re combined with digoxin. If this happens, you might experience lightheadedness, heart palpitations, or extreme tiredness. 

Your healthcare provider may need to adjust your digoxin dosage when starting one of these medications and monitor your blood levels during treatment.

4. Beta blockers

Beta blockers are often used to treat different heart-related conditions, including high blood pressure and heart failure. Some common examples include carvedilol (Coreg), atenolol (Tenormin), and metoprolol (Toprol XL, Lopressor). 

Like certain calcium channel blockers, beta blockers slow down your heart rate. Combining them with digoxin can cause it to slow down too much. Carvedilol can also increase digoxin levels in your blood. Your healthcare provider can determine how to manage this potential interaction in your specific situation. 

5. Other blood pressure medications

There are a few other blood pressure medications that can interact with digoxin. For example, captopril, telmisartan (Micardis), and spironolactone (Aldactone) can increase digoxin levels in your blood.

Loop diuretics (water pills), like furosemide (Lasix) and torsemide, cause your body to get rid of potassium. Sometimes this can cause low potassium levels. And low potassium levels can increase the risk of digoxin toxicity. Low magnesium levels from diuretics also have this risk.

Some of these combinations may be more common, especially if you have heart failure. If they can’t be avoided, your healthcare provider may want to monitor your blood levels more closely or adjust your medication doses during treatment.

6. Cholesterol medications

Some cholesterol medications can interact with digoxin as well. These include statins like atorvastatin (Lipitor) and simvastatin (Zocor). Bile acid sequestrants, like cholestyramine (Prevalite) and colestipol (Colestid), can also interact.

Atorvastatin and simvastatin are used to treat high cholesterol and lower the risk of heart attack and stroke. When taken with digoxin, they can increase digoxin levels. Your healthcare provider may adjust your digoxin dosage with these combinations.

Cholestyramine and colestipol are examples of bile acid sequestrants. They’re also used to lower cholesterol. They work by binding to bile acids (compounds made from cholesterol) in your gut. But they can bind to certain medications, too. This can prevent digoxin from being absorbed, resulting in lower levels in your blood. This can make digoxin less effective.

Your healthcare provider may have you take digoxin at least 1 hour before or 4 hours after taking a bile acid sequestrant. This may be enough to prevent an issue. But they may need to increase your digoxin dosage with this combination.

7. Food and fiber supplements

Sometimes, medications can interact with foods you eat. For example, meals high in bran (a type of insoluble fiber) can lower digoxin levels in your blood. This interaction also applies to over-the-counter (OTC) fiber supplements, like FiberCon and Metamucil. 

Your healthcare provider can tell you how to safely add fiber to your diet if you’re taking digoxin.

8. Certain herbal supplements

St. John’s wort is a supplement that some people take for depression symptoms. It can interact with many medications, including digoxin. When taken together, St. John’s wort can lower digoxin levels. It’s best to avoid this combination. 

But if you’re already taking St. John’s wort, you should talk to your healthcare provider before stopping it. They can safely help you to stop taking it. 

Other herbal supplements, like milkweed and licorice, can have digoxin-like effects on the heart. Taking them with digoxin can lead to higher digoxin levels, and even digoxin toxicity. 

When should I contact my healthcare provider about a digoxin interaction?

Digoxin interactions can result in either higher or lower digoxin levels. They can also have an affect on your heart rate and function.

High digoxin levels can cause digoxin toxicity, which can be life-threatening. Nausea, vomiting, and persistent diarrhea are all common symptoms of digoxin toxicity. But visual disturbances, a fluttering heartbeat, and difficulty breathing can also occur. 

Digoxin is intended to help your heart work properly. If your levels are too low, you might notice new or returning symptoms.

Your healthcare provider will regularly check your digoxin levels to make sure they’re within a safe and effective range. But you should let them know if you notice worsening symptoms, side effects, or signs of digoxin toxicity.

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Written by:

Sarah Lobello Pearson, PharmD

Sarah Pearson is a practicing pharmacist with over 10 years of experience in the field. She received her doctorate in pharmacy from the University of Georgia in Athens, GA.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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