Mixing Meds, Herbs and Supplements Interactions between Medicines, Herbs and Dietary Supplements

The Full Story

Do you take medicines? Lots of people do. Do you also take some type of dietary supplement? If so, you have lots of company there, too.

But do you know how and when those medicines, dietary supplements, and herbs interact with each other? There's a little knowledge and a lot of guesswork about this important topic.

Researchers recently examined the available literature to determine what is actually documented about interactions between medicines, herbs, and supplements. They found 1,491 documented types of interactions between medicines and herbal/botanical products, dietary supplements, and other types of supplements. These involved some combination of 509 different medicines and 213 different herbals/botanicals/supplements.

The medicines most often involved were:

• Warfarin, which is used to prevent blood clots. It interacted with more than 100 types of products and supplements.
• Insulin, which is used to treat diabetes. 
• Aspirin, used to prevent blood clots.
• Digoxin, used to treat heart failure.
• Ticlopidine, another drug used to prevent blood from clotting.

Of the herbal, botanical, dietary supplement, and vitamin products, these were most often cited as interacting with medicines:

• St. John's wort, a plant-based supplement used to treat mild to moderate depression.
• Magnesium, a mineral found in some antacids and laxatives.
• Calcium, a mineral taken for bone strength.
• Iron, a mineral taken for anemia.
• Ginkgo, a plant-based supplement taken for memory problems with memory and other conditions.

Interactions between medicines and supplements can cause a wide variety of harmful effects. The authors listed many of them. To highlight just one, the serious risk of bleeding, consider these interactions:

• People who take warfarin have an increased risk of bleeding if they also take ginkgo, evening primrose, glucosamine, or licorice.
• The risk of bleeding is increased when people take ginkgo along with aspirin, ibuprofen, ticlopidine, and a number of other drugs.

St. John's wort was associated with a number of drug interactions. For example, St. John's wort decreased the effectiveness of calcium channel blockers (used for high blood pressure), digoxin (used for heart failure), doxorubicin (a chemotherapy drug used to treat some cancers), and some contraceptives.

This study emphasizes the importance of discussing ALL of your drugs – prescription, non-prescription, herbal, and dietary supplements – with ALL of your health care providers and pharmacists. Some interactions aren't as serious as those listed above. Even so, recognizing and avoiding such interactions are an important part of staying well.

Take-Home Messages: 

There are nearly 1500 documented interactions between drugs, herbal medicines, and dietary supplements. The most common medicines involved are warfarin, insulin, aspirin, digoxin, and ticlodipine, although there are many others. The most common herbs and supplements involved are St. John's wort, magnesium, calcium, iron, and gingko, though there are many others.

These interactions can cause a wide variety of harmful effects, including bleeding and irregular heart rhythms. Sometimes, taking an herb or supplement changes the way a prescription medicine works in the body. That might cause symptoms like an overdose. Or, it might cause the medicine not to work at all.

Rose Ann Gould Soloway, RN, BSN, MSEd, DABAT emerita
Clinical Toxicologist