Plenty - especially if you are taking herbal remedies without telling your doc. HealthAnswers checks out a few common herbs that can interact fatally with frequently-prescribed drugs for heart, migraine and menstrual complaints.
Chong Pei Lan
Pharmacist
"Natural" Vs "Safe"
Herbal remedies are increasingly being used by some doctors and patients alike either to complement their therapy or as alternative medicines. It is common for people taking herbal products to think of them as "natural" and therefore safe. However, many herbal remedies can interact with prescription medication, with some interactions being potentially fatal. Thus it is important for consumers to be aware of some of these likely hazards of taking herbal remedies.
Terminology
Before proceeding to look at some of the herb-drug interactions, let's define the terms that are used below.
Conventional medicine or western biomedicine is sometimes referred to as allopathic medicine. Allo is derived from Greek, meaning opposite, and pathos refers to suffering. In general, conventional medicine is disease-focused and doctors prescribe the appropriate formula to eradicate the cause or symptom. For example, prescribing antibiotic drugs for bacterial infections or anti-hypertensives for high blood pressure.
Conventional medicine is sometimes referred to as traditional medicine. This is not correct. Traditional systems of medicine existed long before the development of modern western medicine. Western traditions of herbal medicine (also referred to as phytomedicine or botanical medicine) rely primarily on the use of single herbs. Other traditional systems of medicine, particularly Asian traditions, use many herbs in synergistic mixtures or blends. Examples are Traditional Chinese Medicine, Ayurvedic, and Tibetan medicine. The trouble with traditional medicine is that their manufacturing process is not controlled, unlike conventional drugs which are rigorously tested for a long time before they are eventually prescribed, and also very closely monitored when patients are using them.
Herb-Drug Interactions
Several studies of some of the more popular herbal remedies have yielded useful information about drug interactions for the medical workers and patients alike. Here are some of the most commonly known herb-drug interactions:
- St. John's Wort
This herb is used by many for the treatment of mild to moderate depression. While it is said to cause fewer side effects than prescription antidepressants, it has a troublesome side effect of photosensitivity, which will increase the rate of one getting sunburned when taken with other photosensitisers (e.g. tetracyclines).
Patients on prescription antidepressants (e.g. Zoloft) should also avoid taking St. John's Wort as it can lead to serotonin syndrome - a serious condition involving fever, sweating, dizziness and other symptoms.
Recent studies also show that St. John's Wort may potentially interact with other prescription drugs that are metabolised via the cytochrome P450 pathway, leading to suboptimal level of the drugs in the plasma. Such drugs include those used to treat conditions such as heart disease (digoxin) or to prevent conditions such as transplant rejection (cyclosporine) or pregnancy (oral contraceptives).
- Ginseng, Garlic And Gingko Biloba
Ginseng, garlic and Ginkgo biloba (sometimes called the "the three Gs") have all been shown to affect bleeding times.
Ginseng is said to boost energy, reduce stress and the effects of ageing. It has also been used to provide relief from menopausal symptoms.
At least 28 active constituents of ginseng (known as "ginsenosides") have been isolated. Each ginsenoside has a unique pharmacological property and some of these have been shown to inhibit platelet aggregation and the conversion of fibrinogen to fibrin. These are important steps in the process of blood coagulation and taking ginseng with an anticoagulant such as warfarin for heart or stroke-related condition can therefore lead to spontaneous/excessive bleeding.
Garlic is believed to lower cholesterol and reduce blood clot formation in narrowed arteries. Large doses of garlic may increase clotting time as it inhibits platelet aggregation. Thus patients taking warfarin should again refrain from taking garlic.
While Ginkgo biloba has been shown to improve blood circulation, patients on anticoagulant medication such as aspirin, ticlopidine and warfarin should refrain from taking the herb.
Feverfew is marketed commonly as a remedy for migraines. Its proposed benefits have been linked to its ability to inhibit cyclo-oxygenase and phospholipase A2. This property can potentiate the antiplatelet effects of aspirin, leading to spontaneous bleeding. If a woman is also using nonsteroidal anti-inflammatory drugs like Ponstan for painful menstruation or excessive menses, taking feverfew may actually worsen her condition.
Warning: Buyer Beware!
This article is not meant to be exhaustive in its listing of herb-drug interactions, documented or otherwise. Users of herbal medicines should do the following to ensure that they would reap the maximum benefit from the remedy with least possible adverse consequences.
Do your homework - before taking any natural products, learn and find out all you can about it. Though benefits for herbal medicines traditionally rely on single herb, increasingly manufacturers are combining herbs with synergistic effects in a single formulation for marketing purpose. Make sure you know the potential side effects and drug interactions associated with all the herbs listed in the package.
Tell your doctor and other medical professionals about all medications, herbal remedies and supplements that you are taking. This will allow him or her to make correct diagnoses, dispense proper treatment and minimise possible drug interactions.
References:
- Miller LG. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med 1998 Nov 9; 158(20): 2200-11.
- Kim YS, Pyo MK, Park KM et al. Antiplatelet and antithrombotic effects of a combination of ticlopidine and ginkgo biloba ext (EGb 761). Throm Res 1998 Jul 1; 91(1):33-8.
- Janetzky K, Morreale AP. Probable interaction between warfarin and ginseng. Am J Health Syst Pharm 1997; 54:692-3.
- Nancy Roper (ed). Pocket Medical Dictionary (14th edition), Churchill Livingstone, 1987.
Date reviewed: 07 July 2000
