Complementary therapies, such as supplements or aromatherapy, have the potential to benefit patients with cancer, but can also trigger adverse events when they interact with oncology medications. Pharmacists should ask whether patients with cancer are using these products, according to a presentation by Michael J. Schuh, PharmD, MBA, FAPhA, at the Community Oncology Alliance 2019 Community Oncology Conference.

The use of dietary supplements goes back centuries, according to Schuh. Examples of these natural medicines for cancer treatment include periwinkle flower (vincristine/vinblastine) and yew (paclitaxel/ docetaxel). In an interview, Schuh suggested that patients using integrative and complementary therapies should meet 
with a qualified clinical pharmacist familiar with polypharmacy for a comprehensive medication review. This can take place during a medication therapy management consult to check for potential cancer treatment drug interactions.

“Pharmacists don’t always have time to review medications, supplements, or interactions between them in-depth in a dispensing environment with instant demand for prescriptions to be filled, ringing phones, and counseling patients,” Schuh said. He added that this is a valuable service that pharmacists can and should provide for their patients who have cancer.
Herbal Supplements to Watch
Schuh noted several dietary supplements that can interact with oncology medications:

Panax ginseng can interact with the chemotherapy drug imatinib (Gleevec), causing hepatotoxicity. This interaction can happen with other cancer drugs that aremetabolized in the liver as well, such as etoposide, paclitaxel, vinblastine, vincristine, and vindesine. It also effects platelet aggregation, decreases blood glucose, is estrogenic, and increases QT prolongation.

Milk thistle can lead to P-glycoprotein (P-gp) glucuronidation inhibition and increase the absorption of etoposide, paclitaxel, vinblastine, vincristine, and vindesine. It may also alter tamoxifen metabolism.

Red clover can inhibit cytochrome P450 (CYP1A2), CYP2C19, CYP2C9, and CYP3A4; can increase methotrexate levels; can increase bleeding; and is estrogenic, decreasing the efficacy of tamoxifen.

Valerian can, depending on the dose, inhibit CYP3A4 and the UGT1A1 gene; decrease estrogen and irinotecan metabolism; and cause sedation. Schuh noted some patients are already UGT1A1 poor to intermediate metabolizers, so this is a concern.

Turmeric curcumin, a component of turmeric, possibly reduces cyclophosphamide efficacy, which Schuh noted has been linked with the “camptothecin-induced apoptosis of breast cancer cells by up to 71%.” Turmeric curcumin also inhibited apoptosis of breast cancer cells by doxorubicin. Whole turmeric may inhibit mechlorethamine-induced apoptosis of breast cancer cells by up to 70%, enhance the bioavailability of paclitaxel, and induce bleeding if the patient has a low platelet count. It should not be taken 2 weeks before surgery.

Cannabis can inhibit P-gp substrates in etoposide, paclitaxel, vinblastine, vincristine, and vindesine. Tetrahydrocannabinol inhibits P-gp and CYP3A4 and induces CYP2E1 in acetaminophen, chlorzoxazone, ethanol, theophylline, inhaled anesthetics such as halothane and others. In addition, cannabis inhibits platelet aggregation and causes central nervous system depression.

In his presentation, Schuh also discussed supplements that have shown beneficial effects in patients with cancer, specifically lactobacillus and cannabidiols. He noted that lactobacillus has been linked with decreased gastrointestinal discomfort and cannabidiols with reduced pain symptoms. In addition, calcium, beta carotene, and caffeine have been linked to decreasing the risk of cancer.

Schuh also discussed aromatherapy, noting that lavender oil has been linked with some reduction of depression and anxiety symptoms, as well as improved breathing, relaxation, and sleep. However, because lavender has hormonal properties, oral or topical use should be avoided in patients with hormone-sensitive cancers, Schuh explained. Lemon oil has been shown to reduce nausea and lift mood, but it should not be used on the skin since it is phototoxic.

“Oncology pharmacists are in a unique atmosphere, dealing with, on average, more toxic medications than in other settings, so drug interactions, [adverse] effects, and lab monitoring are more important,” Schuh told Directions in Oncology PharmacyTM.

He added that regular patient consultations “would likely increase the chances for better patient outcomes with chemotherapy in the treatment of cancer. To perform these more clinical services would require better third-party payment from insurance companies. However, one may be surprised at the number of patients [who] would be willing to pay for these counseling services.”
Sandra Fyfe, MA


Schuh MJ. Safety of herbals, dietary supplements and aromatherapy in cancer patients. Presented at: Community Oncology Alliance 2019 Community Oncology Conference; April 4-5, 2019; Orlando, FL. thursday/pharmacy/Thurs_1150am_Pharmacy.pdf. Accessed April 5, 2019.