The history of the use of medicinal plants goes back to the Paleolithic age, approximately 60,000 years ago. There is a great deal of written history on the use of herbal treatment in Sumerian, ancient Egyptian, and Greek history. Bronze age Chinese documents record a list of over 200 plants with medicinal properties. This reliance of herbal medicines was all that existed until modern times.

Many of our current medications available to physicians today have a long history of use as herbal remedies, including opium, aspirin, digitalis and quinine. According to the World Health Organization, approximately 25% of modern drugs used in the United States have been derived from plants. There are at least 7,000 medical compounds used in prescribed medication that are derived from plants.

Herbalism (also herbal medicine or phytotherapy) is the study of botany and use of plants intended for medicinal purposes or for supplementing a diet. Even with the advances of synthetic medications, herbalism is still practiced today. Many herbalists are licensed health care practitioners who use herbal supplements to enhance prescription medication, but some have minimal medical training. It is the interface between the use of prescription medication and herbal supplements that can sometimes lead to potentially serious drug interactions.

Commonly used herbal supplements include coenzyme Q-10, danshen, evening primrose, garlic, gingko biloba, ginseng, hawthorn, licorice, saw palmetto and St. John’s wort, melatonin and black cohosh. If a person is not on a prescription medication and uses the supplement at the recommended dose, negative effects are usually minimal. However, with the concurrent use of cardiac, anticoagulants and other prescription and over-the-counter medication, side effects can develop—some potentially serious or lethal. A partial list of potential interactions is shown in the sidebar.

Facts about the regulation of herbal supplements

Most herbal supplements for sale today are not studied in the same way as prescription medication. The Food and Drug Administration (FDA) attempts to oversee herbals, dietary supplements and their manufacturers. The FDA does seize and remove from the market tainted, contaminated, or unsafe dietary supplements when they are aware of problems. Unfortunately, people usually have already been harmed before this occurs.

How a supplement is labeled may be misleading. Terms such as ‘all natural’ and ‘safe’ may not always be true. Even though herbal supplements may be from plant or herb sources, the active ingredients are potent chemicals. Herbal supplements can have drug interactions, even with each other or with food or alcohol. Unfortunately, these products are not always labeled with safety warnings, and it is difficult for a consumer to know if an interaction may occur even if you are not on prescription medication.

Suggestions on the safe use of herbal supplements

Be aware that herbal supplements do contain active chemicals—most with therapeutic benefit, but also some that can set you up for a potentially serious drug interaction, especially if you are also taking a prescription medication.

Inform your physician that you are starting an herbal supplement. Your pharmacist will also be able to check about potential drug interactions and side effects if you are choosing to start an herbal supplement.

If you are not feeling well and suspect a medication problem (e.g., rapid heartbeat, shortness of breath, dizziness, etc.), immediately contact your health-care provider. His or her advice is your best option in preventing serious health effects from any drug interaction.

Do not stop taking your prescription medication unless directed to do so by your doctor. The interaction may be insignificant, and no change may be needed, but the interaction could be serious and the herbal supplement may need to be discontinued.

Potential prescription – herbal supplement interactions*

Coenzyme Q-10 can decrease effectiveness of warfarin and calcium channel blocker, such as diltiazem (Cardizem).

Danshen can interact strongly with certain heart medications, including anticoagulants (such as clopidogrel (Plavix) or aspirin), calcium channel blockers (low blood pressure) and digoxin (risk of irregular heartbeat (arrhythmia)).

Evening primrose may increase your risk of bleeding if you also take an anticoagulant, such as aspirin or clopidogrel or warfarin.

Garlic increases your risk of bleeding if you also take an anticoagulant, such as aspirin or clopidogrel or warfarin.

Gingko biloba increases your risk of bleeding if you also take aspirin or clopidogrel or warfarin.

Ginseng decreases warfarin’s effectiveness.

Hawthorn interacts 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), and digoxin.

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

Saw palmetto increases your risk of bleeding if you also take aspirin or clopidogrel or warfarin.

St. John’s Wort reduces the effectiveness of calcium channel blockers, digoxin, warfarin and statins.

Green tea contains vitamin K and may increase blood clotting.

Cranberry decreases effectiveness of warfarin.

Black cohosh interferes with breakdown of statins (Lipitor), alcohol, and may cause toxicity with acetaminophen (Tylenol).

Echinacea is commonly used in the treatment of the common cold, but interferes with breakdown of caffeine and can lead to jitteriness, headache, or insomnia.

*Source: Mayo Clinic