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Supplements to Avoid During Chemotherapy


By Christina Johnson   |   May 04, 2018

​Chemotherapeutic drugs are strong medications designed to target rapidly dividing cancer cells. If you or a loved one is undergoing chemotherapy, extra care should be taken to discuss the use of any over-the-counter (OTC) medications and herbal supplements with your health care team. 

“Drugs that a person normally takes without much concern can be problematic for a person with cancer,” said Ila M. Saunders, PharmD, an assistant clinical professor at the Skaggs School of Pharmacy and Pharmaceutical Sciences at the University of California San Diego and an oncology clinical pharmacist at UC San Diego Health. “Be sure to discuss everything you are taking with your health care team so they can give you the best treatment possible. Many OTC and herbal supplements can harmfully interfere with chemotherapy treatments.”

chemo drugs

Masking Symptoms

One concern with OTC medications is that they may mask symptoms, indicating a more serious underlying health issue.

"Because some types of chemotherapeutic drugs weaken the immune system, we are always on the alert for signs of infection," Saunders said.

Acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, are often used for pain, but they are also fever reducers. “If you take an OTC medication with acetaminophen or an NSAID, you should tell your health care team,” she said. “They may prescribe another medication that will not mask a fever and still treat your pain.”

Anti-diarrheal medications, such as Imodium (loperamide), are not advised without first talking to your physician. “Your health care team needs to know if you have diarrhea, as it could be a side effect of chemotherapy, a sign of infection or another complication of your treatment or disease," she said.

Changing the Dose

Another concern with OTC medications and herbal supplements is that they can change the effective dose of an oral chemotherapy by altering the drug’s absorption in the gastrointestinal tract.

“Select oral chemotherapies require a certain stomach acidity to be appropriately absorbed," Saunders said.

Prilosec (omeprazole), for example, is a very common OTC proton-pump inhibitor for gastroesophageal reflux disease (GERD). It works by decreasing the amount of acid produced in the stomach. “This means a patient taking Prilosec may get a lower dose of their chemotherapy than that targeted by their oncologist,” she said.

Aloe vera juice is another example. “This herbal supplement has the potential to decrease the intestinal absorption of certain chemotherapeutic agents because it can act as a stimulant laxative and cause diarrhea,” she said.

Dangers of Herbal Supplements

Though some patients with cancer may be interested in complementing or substituting their cancer treatment with herbal supplements, Saunders warns against this.

“In my practice, I discourage herbal supplements in most cases,” she said. “Not only can certain supplements change the efficacy of a person’s therapy, they can also increase their medication’s toxicity.”

Echinacea, curcumin, St. John’s wort, valerian root, and allium (an extract of garlic) — all are examples of herbal supplements that can disrupt the toxicity-efficacy balance of chemotherapy. In addition, the doses of herbal supplements are not standardized. “That being said, the decision to continue or discontinue an herbal supplement is a discussion between the patient and the health care team that takes the goals of treatment and the patient into consideration,” Saunders said.

A more specific herbal supplement-drug interaction is that of green tea extract (EGCG) and Velcade (bortezomib), a chemotherapeutic agent used to treat multiple myeloma, a type of blood cancer.

“EGCG has been shown to reduce the anti-tumor effects of bortezomib,” she said. “Patients on bortezomib are advised to abstain from green tea, especially any green tea extracts.”

Questions to Ask Your Oncology Pharmacist

Saunders encourages patients and family members to talk to their oncology pharmacist about their treatment and ask questions, including:

  • Does my chemotherapy interact with any of my other medications?
  • Does my chemotherapy interact with any foods or beverages, such as grapefruit, grapefruit juice, milk or soda?
  • What herbal supplements, vitamins, or over-the-counter medications can I take safely with this medicine?

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