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Complementary Medications and Chemotherapy
Sharya Vaughn Bourdet, PharmD and Robert Ignoffo, PharmD, Clinical Professor UCSF
Vitamins and Antioxidents
Table Of Contents
The use of complementary and alternative medicine for the prevention and treatment of various diseases has become more popular in recent years than ever before. With the growth of the Internet, consumers now have more accessibility to information and advertising about alternative products. Some people are reluctant to take prescription medications because of fear of unwanted effects. Thus, they turn to dietary and herbal supplements to treat their illnesses because they feel these products are natural and safe. Some individuals may also choose to take both traditional and alternative medicine to treat illnesses, which is especially common in those receiving treatment for cancer. Surveys indicate that 7% to 64% of cancer patients use alternative medicine. However, as many as 50% do not tell their physician that they take alternative therapies,
Several types of alternative therapies exist, including herbals, vitamins, and dietary products. Many of the benefits from these products result from their antioxidant properties. Antioxidants have received much media attention in recent years regarding cancer prevention. A diet rich in fruits and vegetables, which are good sources of antioxidants, has been reported to lower a person's risk for some types of cancer. Antioxidant supplements, which contain larger amounts of antioxidants than contained in food sources, have also been reported to decrease a person's risk of developing certain types of cancer. Specifically, vitamin E and selenium supplements have been shown to reduce the incidence of prostate and colon cancer.
Antioxidants are also used by some patients during cancer treatment in the hopes of reducing the side effects of chemotherapy. Two prescription antioxidants, Mesnex® (mesna) and Ethyol® (amifostine), are available which specifically prevent certain side effects of cancer agents such as ifosfamide, cyclophosphamide, and cisplatin. Since these two antioxidants are for prescription use only, they have been evaluated in human studies by the Food and Drug Administration (FDA) and found to not reduce the effectiveness of cisplatin, cyclophosphamide, or ifosfamide in the treatment of cancer. Non-prescription antioxidant supplements are considered to be dietary products and are not regulated by the PDA. Human studies showing the impact of dietary supplements on chemotherapy effectiveness are not required for these products to be sold in the United States.
There are many different chemotherapeutic agents used to treat cancer. Most of the agents can be grouped into classes based on how they work against cancer cells. Several classes of chemotherapy work by producing a reactive oxygen compound or free radical. Free radicals can damage proteins or other structures within cells which leads to the death of the cell or an inability to divide and make new cells. Table (1) shows the common chemotherapy agents that work by producing free radicals. While cancer cells are the main target of chemotherapy, normal cells may be affected as well, causing side effects such as hair loss, low blood cell counts, and mouth sores.
Table 1: Chemotherapeutic Agents Producing Free Radicals
- Alkylating agents
doxorubicin (Adriamycin®, Doxil®)
- Podophyllum agents
Antioxidants are compounds that bind and inactivate free radicals. Free radicals are normally produced from many of the body's everyday stresses such as inflammation, exercise, alcohol, ultraviolet light, and fatty diets. A healthy diet complete with fresh fruits and vegetables provides enough dietary antioxidants to inactivate the normal production of free radicals. Antioxidant supplements, which contain mega-doses of antioxidants, are available in many health-food stores and pharmacies. Table (2) lists some common antioxidants that may be found in dietary supplements. Antioxidants may decrease chemotherapy-induced damage of normal cells by inactivating free radicals, but the same damage may also be decreased in cancer cells. Therefore, doses of antioxidants that are larger than that provided in a normal diet may potentially interfere with the effectiveness of certain chemotherapy agents by reducing their action in cancer cells.
Table 2: Common Antioxidants Found in Dietary Supplements
- alpha lipoic acid
- grape seed extract
- vitamin A
- vitamin C (ascorbic acid)
- vitamin E (alpha-tocopherol)
- coenzyme (CoQlO)
The combination of antioxidants and chemotherapeutic agents may present some potential problems to the patient and health care provider. First, many patients do not tell their physician they are taking antioxidants because they fear disapproval from the physician or have never been asked about such therapies. Second, the use ofantioxidant supplements during chemotherapy has not been studied to assess long-term effects such as safety or survival. Since no such scientific studies have been conducted, the potential interactions between antioxidants and chemotherapy must be predicted from currently available knowledge.
Patients should fully understand the possible consequences of combining antioxidant supplements and chemotherapy. Based on the current knowledge available, there is a potential reduced effectiveness of certain chemotherapeutic agents when combined with antioxidants. This means that patients may not receive the full benefit of cancer treatment. Whether a reduced benefit corresponds to therapy failure such as a lack of clinical response, continued progression of the cancer despite therapy, or decreased long-term survival has not yet been determined. Patients and physicians should be aware that combining antioxidants with chemotherapy may improve side effects in the short-term but may hinder long-term survival or clinical response. Patients and physicians should decide on a course of action that ensures maximum clinical benefit yet embraces the patient's wishes regarding therapy. This plan may include the decision not to take antioxidants and chemotherapy at the same time, to find chemotherapeutic agents that have no possible interaction with antioxidants, or not to take antioxidants at all during cancer treatment.
It is important that patients and health care providers be informed about all possible interactions between dietary supplements and medications. This means that health care providers should ask patients about the use of alternative therapies and that patients should be open and honest with providers when asked. Patients and physicians should jointly decide a plan of action for using alternative therapies that will achieve the goals of both the physician and patient. New information concerning alternative therapies is continually becoming available. Possible interactions between therapies such as antioxidants and chemotherapy should be re-evaluated once more information is available and long-term clinical studies have been conducted.
In the meantime, the following are specific recommendations for those cancer patients who are taking antioxidant supplements or herbal medications. taking antioxidant supplements or herbal medications.
- Inform your doctor(s) that you are currently taking dietary or herbal products. In order for your doctor to keep an accurate list of medications, it may help to bring the products or a list of ingredients and doses with you at your office visits.
- Keep your doctors) updated if you start any new dietary or herbal products.
- As a general rule, discontinue taking antioxidants the day before, during, and the day after receiving chemotherapy.
- Antioxidants are available in many forms including vitamin, mineral, and herbal supplements. If you are not sure if a dietary supplement that you are taking contains an antioxidant, ask your doctor or pharmacist.
For further questions about the use of dietary supplements, you may wish to consult the following references.
- Labriola D, Livingston, R. Possible Interactions Between Dietary Antioxidants and Chemotherapy, Oncology 13(7); 1003-7,1999.
- http://www.nci.nih.gov (Sponsored by the National Cancer Institute)
- http://nccam.nih-gov (Sponsored by the National Center for Complementary and Alternative Medicine)
- http://www.cancer.org (Sponsored by the American Cancer Society)
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The use of herbal medications is a common occurrence in patients being treated for cancer. They are touted for their medicinal properties and may be useful for treating some of the side effects associated with chemotherapy. However, being derived from botanicals, some herbal products may have impurities (bacteria, fungi, or parasites) that could put patients at risk for infections during the period of decreased white blood counts. In addition, some herbal preparations have adverse effects of their own that may worsen toxicities from high dose chemotherapy (see list below). These are absolutely contraindicated because of these serious side effects. Thus, many institutions advise patients to discontinue herbal and nutrient supplements before and during chemotherapy because of these risks.
There are claims by Chinese herbalists that many of their preparations may be helpful in minimizing side effects of chemotherapy. They may work through the same antioxidant mechanisms described for the vitamin preparations. Further study is necessary to determine if they may affect the efficacy of some chemotherapy regimens. In addition many studies are underway in the United States to determine whether traditional Chinese herbal medications are beneficial in improving patient quality of life while receiving chemotherapy.
Contraindicated Herbals Herbal Toxicity Chinese/oriental herbs Unknown active ingredients Chaparral Hepatoxicity Cleansing Herbal Dietary Supplement Contains digitalis glycosides Ephedra or Ma Huang High blood pressure Jin Bu Huan Hepatitis Laetrile Carcinogenic, cyanide poisoning Mistletoe Extract (Iscador) Nausea, bradycardia, gastritis, hypertension Pau d'arco Anticoagulant bleeding Pennyroyal Hepatoxic Plantain Extracts, nature Cleanse tablets,
Botannical Cleanse Tablets, Blessed herbs
Contaminated with digitalis glycosides Siberian ginseng Contains male hormone-like chemicals
Acceptable Herbals Herbal Therapeutic Use Blackberry, raspberry tea Diarrhea Fanugreek seeds Diarrhea Ginger tea, cookies Nausea or Vomiting Cinnamon Nausea Peppermint tea Diarrhea St John's wort Depression Urinary Obstruction or enlarged prostate Saw Palmetto Valerian Insomnia Kava Insomnia
From Cassileth: Cancer Nursing 22:85-90, 1999
References on Herbal Medications:
- Cassileth B. Complementary Therapies: Overview and state of the Art. Cancer Nursing22:85-90,1999
- The Complete German E Commission Monographs. Therapuetic Guide to Herbal Medications. M. Blumenthal,ed. American Botanical Council, Boston Mass, 1998
- Tyler Varro: Herbs of Choice. Therapeutic Use of Phytochemicals.
- Tyler's Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies by Steven Foster and Varro E. Tyler
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