By Andrew Gaeddert
Recently, much concern has been raised regarding herb-drug interactions. This is not surprising. The number of persons using dietary supplements, including herbal products, has increased rapidly during the past decade. Surveys conducted in recent years suggest that nearly one quarter of Americans use herbal products.1, 2 Estimates suggest that 25% of this population use such products along with prescription medications, and that many (47%-72%) do not tell their health care provider (MD) of herbal product use.2 One of the major reasons is that patients are uncomfortable with informing their MDs because they feel their MD will be unsympathetic. This lack of sympathy is due to several reasons. The fundamental reason is perhaps most MDs are not trained in even the basics of herbal medicine. Therefore, MDs are reluctant to encourage the use of a modality they know nothing about. Furthermore, matters are not helped with the often skewed information about herbs in the professional literature. While more and more MDs are becoming educated about herbs and other supplements, a vacuum of knowledge still exists among these professionals. This absence of knowledge has left their patients pretty much on their own, unless these patients consult a complementary healthcare practitioner familiar with the use of herbs. Thus, as such practitioners we should be proactive about filling this vacuum by educating ourselves and our clients about the concomitant use of herbs and medications, and possible herb-drug interactions.
One of the common misperceptions about herbs, even among some practitioners, is that because they are derived from natural sources, they are always safe and harmless. While it is true that when herbs are taken individually or in appropriately formulated combinations, and in the correct dosages, few, if any, side effects result. Herbs used inappropriately can have unwanted effects. This is in comparison with prescription medications, of which nearly all have adverse effects of one kind or another. But what happens when herbs are used along with pharmaceutical medications? Are the herbs still considered innocuous because they’re “natural” and won’t react with the medications? Incidents of herb-drug interactions are being reported more frequently in the professional literature. Some of these cases appear to be attributable to the herbal product, because when it was stopped, symptoms subsided and blood parameters returned to levels prior to taking the herbal product. However, with some incidents, it is not so apparent that the herbal product is to blame since there may have been other confounding factors, including multiple medication use, responsible for the observed reaction.
An important step that practitioners should take in becoming more knowledgeable about herb-drug interactions is recognizing that herbs have pharmacological effects. Thus, when we encounter clients who take prescription medications and ask for an herb to address the same symptoms, we should consider carefully whether or not to fulfill their request. Even when clients ask for herbs for other problems, it is wise to exercise the same prudence.
In simple terms, an interaction occurs when a substance reacts with another, either increasing or decreasing the effects of one of the substances. In pharmacologic terms, interactions fall into two general categories: pharmacokinetic and pharmacodynamic. Pharmacokinetic interactions are caused by changes in a substance’s absorption, distribution, metabolism, or excretion. These are quantitative changes in that the amount and duration of a substance’s availability at the site of action (receptor sites) have been altered. Pharmacodynamic interactions are due to changes at the receptor level. These are qualitative changes in that the resulting interaction can be additive or opposing in nature.
DESIRABLE INTERACTIONS
In this article, we are primarily concerned with the undesirable inter- actions between medications and herbs. However, it should be mentioned that some interactions are actually desirable. In the world of pharmaceuticals, bronchodilators are often paired with corticosteroids in the treatment of asthma. The former address the symptoms of airflow obstruction, and the latter treat the underlying process that causes airway obstruction. By using both together, the therapeutic effects of treating asthma are enhanced.
In traditional Chinese medicine, the interactions among the different medicinal substances making up an herbal formula are what make it effective. In fact, it is because of these interactions that the formula essentially becomes a “therapeutic agent that can treat much more effectively and completely than can a single substance.”3 Very rarely are single substances used in Chinese medicine. This is because each has its strengths and shortcomings. By combining substances, the strengths of each are promoted and the shortcomings (in the form of side effects) are ameliorated. For example, licorice is often added to a formula because it is able to moderate and harmonize the properties of the other herbs. It is also used as an antidote for many toxic substances.
Another kind of desirable interaction is the use of herbals to reduce the side effects of chemotherapy and radiation therapy during cancer treatment. This kind of combined traditional and western treatment is standard for cancer therapy in China. In our own clinic, we have found that by using the Health Concerns formula Quiet Digestion, patients undergoing chemotherapy have fewer episodes of intestinal upset. Use of single herbs have also been found to produce beneficial interactions. Clinical trials with milk thistle seed have found that its concentrated extract is helpful in preventing liver damage in patients undergoing therapy with hepatotoxic psychotropic medications.4
Bromelain (papaya enzyme) improves the effects of antibiotics as well as of chemotherapy drugs.5
UNDESIRABLE INTERACTIONS
As more and more research is completed on the chemical makeup of herbs, we will become better at giving informed advice to clients about taking herbs with medications. For example, from recent research on ginkgo, it appears that properties in ginkgo delay or prevent collagen-mediated blood clot formation.6
This, then, may explain ginkgo’s apparent interaction with blood thinning agents such as warfarin and aspirin—a pharmacodynamic interaction that results in an additive effect with a negative consequence. Another example of potential pharmacodynamic interactions are those that may occur between sedative herbs such as kava and sedative (sleeping) medications.
Alteration of a substance’s absorption can result from pharmacokinetic interactions. An example of such an interaction may result when bulking agents such as psyllium or herbal laxatives like Senna are taken with medications. Bulking agents and laxatives speed up gastro-intestinal motility, thus potentially reducing absorption of medications in the gut.
Another kind of pharmacokinetic interaction results from altered elimination of a substance. For example, herbal diuretics like licorice, cornsilk, and dandelion may cause the toxicity levels of medications like lithium or digitalis to rise. Diuretics promote urine formation, thus increasing the concentration level of medications in the body.
USING HERBS AND MEDICATIONS SAFELY
First, you as a practitioner and your client should know exactly what medications he or she is taking and the reasons for taking them. Many individuals, particularly seniors, are on several medications at a time. Therefore, practitioners should be proactive in asking about medications so that when natural remedies are used, potential interactions can be avoided. It may even be helpful to schedule an entire appointment just to discuss how herbs and medications can be used together safely, and to ensure that you and your client are comfortable with the proposed treatment plan. It may also be wise for the client to stop all self-administered natural products to steer clear of confounding results. Seeking the advice of a trained herbalist is always a good idea to help streamline the treatment.
Second, if the client is in fact on several medications concurrently, it’s advisable for either the practitioner or the client to discuss the case and medications with the primary care provider (PCP). Although some PCPs are not amenable to their patients using natural products, an increasing number are more accepting of the concept, and willing to work with complementary healthcare providers. While the goal of recommending natural products is to be able to stop the use of pharmaceuticals, however, this may be difficult to achieve. In many instances, the best that can be done is a reduction in dosage of the medications. Therefore, in reducing the dosage of medications, the client’s PCP should be consulted.
Third, when using herbs concurrently with medications, practitioners should advise clients to take herbs at least two hours apart from medications, and to comply with any additional instructions.
AVOIDING “DUPLICATION” OF EFFORT
A general principle to keep in mind when using herbs with medications is to not “duplicate” efforts. This means that if an individual is on a particular medication, it’s best not to recommend an herb or formula with the same therapeutic effect. For example, if the client is using an allergy medication containing ephedrine, it’s probably wise to not recommend an herbal formula that contains ma huang. With antibiotics, herbs with antibiotic effects should probably not be recommended concomitantly to treat acute infections to avoid possible interactions. However, if the individual has been taking an antibiotic long-term and the medication is ineffective, the client should be advised to ask the prescribing physician for evaluation of whether another antibiotic would be more appropriate. In this case constitutional herbal therapy may be very helpful.
Another commonly encountered set of clients are those who are on monoamine oxidase (MAO) antidepressants, and request herbs because they want to stop using the medications. While it is unclear at this time whether certain herbs interact with MAO inhibitors, it is probably prudent to not recommend herbs to this population because of the high risk of potential interaction with these medications. I was recently asked to recommend herbs for a young man who was on both an antidepressant and antipsychotic medications. I decided against taking on this client for both his safety and mine. Another group of patients to be aware of are those who are using recreational substances, such as alcohol, pharmaceuticals, and marijuana. Often, these individuals will report that the herb(s) they received is causing a problem when in fact it is their use of alcohol or marijuana. If they are not forthcoming in revealing this, the practitioner may need to tactfully ferret out the information.
NOTES
- Williamson JS, Wyandt CM. The herbal generation: Legal and regulatory considerations. Drug Topics, 19:101-110, 1999.
- Eisenberg DM, Kessler RC, Foster C, et al. Unconventional medicine in the United States. New England Journal of Medicine, 328:246-252, 1993.
- Bensky D, Barolet R. Chinese herbal medicine: Formulas and strategies, 14.
- Palasciano G, Portinacasa P, Palmieri V. et al. The effect of silymarin on plasma levels of malon-dialdehyde in patients receiving long-term treatment with psychotropic drugs. Current Therapeutic Research, 55:537-545, 1994.
- Neurauer RA. A plant protease for potentiation of and possible replacement of antibiotics. Experimental Medical Surgery, 19:143-160, 1961.
Andrew Gaeddert is an herbalist and author of the books, Healing Digestive Disorders and Chinese Herbs in the Western Clinic.