Herbal Supplements and Medications: an Overview of Herb-herb and Drug-herb interactions
The Risk for Drug-Herb Interactions is Not Trivial
Herbal supplements, vitamins, and dietary supplements are widely used. Depending on the study you look at, 25-85% of people who see doctors at a given time are using herbal supplements. About 15 million adult Americans are at risk for possible adverse interactions between prescription drugs and herbs or high dose vitamins, according to the Journal of the American Medical Association. A British study (2003) found that of the 62% who took herbal preparations, 1 in 20 were taking a potentially dangerous combination. How can you make sure you're not at risk?
The 20,000 or so herbal supplements that are on the market in the US alone only come under the direct scrutiny of the FDA if there is a problem, or when a product is selected for spot-checking. While information about interactions is increasing rapidly, it is still quite limited. The best sources of information are your pharmacist or your physician, although be aware that for many of these products, the information is simply not yet known.
Twenty Herbs and Five Classes of Medications that can Interact
This is not an exhaustive analysis of herbal supplements, but an overview of some of the more common herb and drug combinations that can affect the headache sufferer.
"Well, I don't take barbiturates!" you might think to yourself indignantly. Except that you do if you take Fioricet® or anything else with butalbital in it. Combining this with kava kava can cause undue sedation. It should also be noted that there have been reports of liver failure from kava kava alone, and taking it in conjunction with acetaminophen (or paracetamol) is not wise, as this enhances risk to the liver.
Calcium channel blockers
Calcium channel blockers taken in combination with dong quai can drop blood pressure significantly. So can taking hawthorn leaf. The combination of verapamil and guarana can cause hyperstimulation of the nervous system. Gingko can inhibit the metabolism of diltiazem.
SSRI antidepressants such as Prozac, Paxil, and Lexapro should not be taken in conjunction with St. John's wort as this can result in serious side effects. St. John’s wort acts on the same brain receptors as these medications.
St. John's wort should also not be taken with tricyclic antidepressants (amitriptyline, nortriptyline, doxepin, imipramine, desipramine, protriptyline) as it can reduce the effective level of drug in your system. With high enough doses, serious side effects can occur.
Lisinopril, ramipril, and other ACE-inhibitors are sometimes used off-label as migraine preventative medications. Combining them with cayenne, used internally, can increase the risk of cough sometimes seen as an adverse effect of the ACE-inhibitors.
Aspirin and anti-inflammatories
There is a wide range of herbs that interact with the coagulation process. Most of these cause bleeding by interfering with the platelets (clotting cells). In small doses, this effect can be desirable. It's why a baby aspirin is recommended in older individuals for cardiovascular protection. However, if you use these herbals in combination with one another or with pharmaceuticals that have a similar effect, you may discover—the hard way—that you have gone far beyond any desirable goal.
The four most commonly used herbs that interact with blood clotting are known as the Four G's: Ginger (also called sheng jiang, shen jing, palu, shokyo, or shoga), Garlic, Ginkgo biloba (also called maidenhair or kew tree), and Ginseng (sometimes called Panax; Siberian ginseng is also known as Eleutherococcus). Many headache sufferers take aspirin-containing analgesics or other nonsteroidal anti-inflammatory medications (especially indomethacin) and should know of the potential for interactions that can result in bleeding. In the case of migraine, it should be the Four G's and an F, because feverfew falls into this category as well.
Other herbs with anti-coagulant properties are chamomile, dong quai (or tang kuei), and horse chestnut. Other anti-platelet herbs are: bilberry, bromelain, cayenne, flaxseed oil, green tea, meadowsweet, motherwort, turmeric, and willow.
Make Sure You are not at Risk for Interactions
Be safe, not sorry. If you are taking more than one medication, the possibility for interactions increases greatly. Drug-drug interactions are already an issue for many people, especially for those who have more than one prescribing provider. If you are also taking herbal supplements, it increases the potential for further drug-herb interactions. Talk to your pharmacist if you have any concerns about this; they are far more qualified to answer your questions than the clerk at the health food store.
What Should I Do If I'm Worried About Drug-Herb Interactions?
If you are concerned that you might be experiencing an adverse reaction to a vitamin, mineral, or herbal supplement, talk to your health care provider. Some of these reactions are predictable symptoms related to taking too much. Others may be due to contaminants in a product, or due to a drug-herb interaction. If your doctor or health care provider is not certain, a call to your pharmacist may be helpful. Databases listing this information are being updated frequently. It’s important to let someone know if you think you are having a reaction. Adverse reactions to supplements are supposed to be reported to MedWatch which is a reporting program of the FDA. That way, accurate information can be collected. This can be helpful to someone else in the future.
by Christina Peterson, M.D.