Drug Interactions between pazopanib and Sambucol

MONITOR: Coadministration of elderberry and pazopanib may increase the risk of pazopanib-related adverse effects. This interaction was suspected in a case report involving a 65-year-old woman diagnosed with localized intermediate-grade sarcoma initiated on pazopanib 400 mg orally daily while taking elderberry supplements at an unknown dose. Pazopanib was increased to 800 mg orally daily after one week. By week three on pazopanib, the patient reported intense nausea and frequent loose stools, requiring treatment and by the fourth week, laboratory tests indicated grade 3 liver injury. All medications, including elderberry supplements, were stopped and within four weeks, liver enzymes returned to baseline. At this time, pazopanib treatment was resumed at a lower dosage of 400 mg orally daily without the recurrence of adverse effects or liver injury. Although clinical evidence is limited, the potential mechanism for this interaction may be due to elderberry mediated inhibition of CYP450 3A4 which may occur at higher doses and lead to increased pazopanib exposure.

MANAGEMENT: Caution is advised if elderberry is used concomitantly with pazopanib. If coadministration is required, patients should be more closely monitored for pazopanib-related adverse effects such as hepatotoxicity, nausea, vomiting, and diarrhea.