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Why is it Risky for Cancer Patients to take Herbal Products Concomitantly with their Chemotherapy?

Jan 15, 2020


Greater than 50% of cancer patients use herbal products concomitantly with their chemotherapy to help reduce the side-effects of the chemo ( as a natural remedy). If not chosen scientifically, this can increase the risk of adverse herb-drug interactions that have the potential to interfere with the cancer chemotherapy. The herb-drug interactions can either reduce the efficacy, or increase the toxicity and side-effects of the chemo used in cancer.

Chemotherapy treatments are part of most cancer therapy regimens as a first line standard of care as per evidence based guidelines. Based on all the posts and blogs of patients’ experiences during chemotherapy, there is an apprehension amongst patients due to the impending side-effects they will have to deal with. Hence, cancer patients often take different herbal supplements (as a natural remedy for cancer) based on referrals from friends and family or what they read on the internet, to help alleviate the side-effects and improve their general well being.

Can we use Herbal products along with Chemo in Cancer as a natural remedy? Herb-drug interactions

There is data in the US alone based on a 2015 National consumer survey where 38% of prescription drug users report simultaneous use of herbal products with the largest number of these being stroke patients (48.7%) and cancer patients (43.1%), besides others (Rashrash M et al, J Patient Exp., 2017). An earlier study had reported a prevalence of 78% of patients using herbal products while on chemotherapy (McCune JS et al, Support Care Cancer, 2004). And a more recent study found that more than half of the respondents reported use of herbal products along with chemo (Luo Q et al., J Altern Complement Med., 2018). Hence the data indicates that there is a large number of cancer patients taking herbal products while on chemotherapy treatment and this is something that has the potential to cause them harm.

The key reason why concomitant use of herbal products along with chemotherapy can be harmful is due to herb-drug interactions. It is more risky in patients with chronic and complicated conditions taking multiple medicines.

What is herb-drug interaction and how can herbal products cause issues with chemotherapy?

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  • Herb-drug interaction can occur when the herbal product interferes with the metabolism or clearance of the drug from the body. The metabolism/clearance of drugs is mediated by drug metabolizing enzymes from the cytochrome P450 (CYP) family and drug transport proteins.
  • These interactions can alter the concentration of the drug in the body. Chemotherapy drugs, with known issues of toxicity and severe side-effects, are dosed at their established effective and safe, maximal tolerated level, where the benefit of the drug outweighs the risk. Any changes to the concentration of the chemotherapy drug in the body can cause the drug to be either ineffective or cause increased toxicity.
  • Herb-drug interactions can occur due to the inhibition or activation by the herbal phytochemicals of these drug metabolizing CYP enzymes or drug transport proteins. Some chemotherapeutic agents need to be activated by the CYPs to be effective. With inhibition of CYPs, such drugs that need to be activated will be rendered ineffective.
  • There could be herb-drug interactions that result in increased clearance of cytotoxic drugs due to CYP activation, that could lead to sub-therapeutic drug exposure and could lead to therapy failure.
  • Some herb-drug interactions due to CYP inhibition could lead to accumulation of cytotoxic drugs due to delayed clearance and can increase the drug toxicities due to high drug doses.
  • Cancer patients are already taking multiple medications simultaneously due to other cancer associated conditions and comorbidities, that have a risk of drug-drug interactions. Use of herbal products can further increase the risk of these potentially harmful interactions that interfere with the drug impact.

Clinical studies have indicated several herbal products including St. John’s wort, gingko, ginseng, licorice, kava, garlic, cranberry, grape seed, germander, goldenseal, valerian, and black cohosh among others to inhibit or induce CYPs (Fasinu PS and Rapp GK, Front Oncol., 2019). Patients need to be aware of these potential harmful issues before taking supplements randomly without sufficient knowledge and supportive data. Thus natural supplements should be chosen carefully and scientifically to have the desired beneficial impact.

Cancer patients often have to deal with different chemotherapy side effects which affect their quality of life and look out for alternative therapies for cancer. Taking the right nutrition and supplements based on scientific considerations (avoiding guesswork and random selection) is the best natural remedy for cancer and treatment related side-effects.