Herbal supplements are natural, so they must be safe, right? Not necessarily.

Herbal supplements can have strong effects in the body. Some can interact with prescription medications used to treat heart and circulatory problems, such as high blood pressure and heart failure. Some of these interactions can even be dangerous.

Herbal supplements and prescription medications

About one-half of adults in the United States report having used at least one dietary supplement in the previous month. But research suggests that only about 34 percent of people taking an herbal supplement tell their doctors about this use — and most of those people also are taking a prescription medication.

Yet many herbal supplements may interact with medications for cardiovascular disease. For example, several popular herbal supplements interact with the blood thinner warfarin (Coumadin, Jantoven).

Here are just a few of the herbal supplements that can affect warfarin:

• Danshen
• Licorice
• St. John's wort

There are several others. That's why it's so important to talk with your doctor before taking herbal supplements if you take prescription medications. Your doctor and pharmacist can help you avoid risky interactions.

Herbal supplements and drug interactions

Several popular herbal supplements interact with common heart medications. This list covers only some interactions. It's important to talk to your doctor before taking any herbal supplements if you take prescription medications.

Coenzyme Q-10

Taking coenzyme Q-10 can decrease:

• The effectiveness of warfarin
• Your blood pressure if you also take a calcium channel blocker, such as diltiazem (Cardizem, Dilacor XR, others)

Danshen

Danshen can interact strongly with certain heart medications, including:

• Anticoagulants. Taking danshen significantly increases your risk of bleeding if you also take warfarin or another anticoagulant, such as clopidogrel (Plavix) or aspirin.
• Calcium channel blockers. Taking danshen increases your risk of low blood pressure if you also take diltiazem or another calcium channel blocker.
• Digoxin (Lanoxin). Taking danshen increases the effects of digoxin — which is used to treat a variety of heart conditions — and puts you at risk of irregular heartbeat (arrhythmia).

Evening primrose

Evening primrose may increase your risk of bleeding if you also take an anticoagulant, such as:

• Aspirin
• Clopidogrel
• Warfarin

Garlic

Garlic increases your risk of bleeding if you also take an anticoagulant, such as:

• Aspirin
• Clopidogrel
• Warfarin

Gingko biloba

Ginkgo biloba increases your risk of bleeding if you also take:

• Aspirin
• Clopidogrel
• Warfarin

Ginseng

Taking ginseng with warfarin decreases warfarin's effectiveness.

Hawthorn

Hawthorn might interact with:

• Beta blockers, such as atenolol (Tenormin), nadolol (Corgard) or propranolol (Inderal LA, Innopran XL)
• Calcium channel blockers, such as diltiazem, nifedipine (Procardia) and verapamil (Calan, Verelan)
• Nitrates, such as nitroglycerin (Nitrostat, Nitro-Dur, others) and isosorbide (Dilatrate-SR, Isordil)
• Digoxin

Licorice

Licorice decreases levels of warfarin and can increase the effects of digoxin.

Saw palmetto

Saw palmetto increases your risk of bleeding if you also take:

• Aspirin
• Clopidogrel
• Warfarin

St. John's wort

Taking St. John's wort reduces the effectiveness of:

• Calcium channel blockers
• Digoxin
• Warfarin
• Statins, such as atorvastatin (Lipitor), lovastatin (Altoprev) and simvastatin (Zocor)

Playing it safe with herbal supplements

If your doctor tells you it's OK to use an herbal supplement combined with a medication, make sure you follow dosing instructions carefully. Watch for any unusual signs or symptoms that you could be having a drug interaction, such as:

• Rapid heartbeat
• Changes in blood pressure

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Sept. 16, 2017 See more In-depth