Elderberry interaction with pazopanib in a patient with soft‑tissue sarcoma: A case report and literature review

Elderberry flower extract is marketed as an herbal supplement with purported benefits in boosting the immune system. The use of elderberry increased during the coronavirus pandemic. However, the interaction of elderberry with cytotoxic medicines has remained elusive. Pazopanib is a multikinase inhibitor approved for patients diagnosed with soft-tissue sarcoma. The present study reported on the case of a middle-aged woman diagnosed with localized intermediate-grade sarcoma of the left sartorius muscle who received neoadjuvant pazopanib with radiation therapy. The patient had no other medical comorbidities and only took over-the-counter (OTC) elderberry supplements for numerous years to 'boost' her immune system. She started pazopanib at 400 mg per os (PO) daily, which was increased to 800 mg PO daily after a week. By week three on pazopanib, the patient reported intense nausea and a number of loose stools, requiring anti-nausea medication. By the fourth week on pazopanib, laboratory tests showed grade 3 liver injury, as demonstrated by a fivefold rise in liver enzymes along with severe nausea and loose stools. All medications, including elderberry supplement, were stopped. Within two weeks of stopping all medicines, the liver enzymes started normalizing within two weeks and were normal by the end of four weeks. Pazopanib treatment was resumed without the recurrence of side effect. Pazopanib is metabolized in the liver via the cytochrome P 450 (CYP)3A4 enzyme pathway. Hence, potent inhibitors of CYP3A4 are avoided for concurrent use with pazopanib. Small in vitro studies on elderberry extracts have shown weak inhibition of CYP3A4. However, considering the wide usage of elderberry and the availability of mixed supplements OTC, it is essential to pursue clinical studies in cancer patients to understand the interactions of elderberry extracts with cytotoxic medicines. In this report, the scientific evidence behind the use of elderberry was reviewed and a hypothesis of its interaction with pazopanib was proposed.