We sometimes think of herbs as innocuous products that we can take freely without worry because they are natural and can’t do any harm. While it’s true they are natural and in a healthy body are unlikely to do harm unless taken in huge quantities, for someone who is already taking a pharmaceutical, there can be unpleasant consequences.
Even foods can interact with pharmaceuticals and either reduce or increase the effectiveness. Alcohol is the most frequent example of a food that interacts with many drugs. More surprising are citrus fruits and juices. For instance, grapefruit will reduce the effectiveness of some epilepsy medicines and is considered dangerous for people taking Zocor, a cholesterol drug.
Anyone taking a pharmaceutical should become familiar with the foods, over-the-counter medications, and herbs that could change the effectiveness of the medication. Make a list of products or foods that should be avoided and put it in your wallet or purse.
Discuss any new herbs with your doctor before you start taking them. Doctors are not experts on herbs but they will be aware of those that can cause problems for your pharmaceuticals.
Here’s a list of some serious interactions between drugs and herbs. This is not a complete list; it is included to give the reader a sense of how serious these interactions may be.
- Hawthorn is an excellent heart tonic but when combined with some other heart medications it can cause heart attack and death.
- Ginseng is a name given to several different herbs. Some forms of it can increase blood pressure. When taken with Coumadin, it can cause internal bleeding. Ginseng is not recommended for pregnant or breast-feeding women.
- Garlic can interact with diabetes medicines to produce a dangerous drop in blood sugar. It can also increase the effectiveness of anticoagulant medicines making bleeding difficult to stop.
- Goldenseal is useful for short periods to avoid colds but can’t be taken long-term. It also interferes with betablockers and medicines for diabetes and kidney disease.
- Feverfew is commonly taken for migraine headaches but if the patient is also taking Imitrex it can cause dangerous increases in blood pressure.
- Kava kava is an antianxiety herb that shouldn’t be combined with antidepressants or antipsychotics.
- St. John’s Wort contains hypericin which acts like an MAO inhibitor. It reduces the effectiveness of antiepileptics, antiretrovirals, benzodiazepines, oral contraceptives, immunosuppressant drugs, and more. Note that it can reduce the effectiveness of birth-control pills by 50%! St. John’s Wort can cause very dangerous reactions when taken with foods high in Tyramine—some cheeses, chicken liver, red wine, processed meats, dried or pickled fish, beans, soy sauce, ale or beer.
Two books that give a complete description of herbs and their interactions are PDR for Nonprescription Drugs, Dietary Supplements, and Herbs, 2008, and PDR for Herbal Medicines.
