Bortezomib Intravenous and Multivitamins with minerals

Talk to your doctor before using bortezomib together with multivitamin with minerals. Supplements that contain ascorbic acid, or vitamin C, may reduce the effectiveness of bortezomib in treating your cancer. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

GENERALLY AVOID: Preliminary data suggest that ascorbic acid may diminish the antitumor effects of bortezomib when taken simultaneously. In vitro, ascorbic acid has been shown to inhibit several biologic activities of bortezomib, including induction of apoptosis and G2-M cell cycle arrest and inhibition of proteasome activity, presumably by forming a complex with bortezomib that is both inactive and has poor membrane permeability into cells. A group of investigators showed that plasma from healthy volunteers taking 1 gram of vitamin C per day reduced bortezomib-induced multiple myeloma cell death in vitro. Using a mouse model of human multiple myeloma, they also found that oral vitamin C (40 mg/kg/day) blocked the inhibition of tumor cell growth induced by bortezomib (0.1 mg/kg twice a week for 4 weeks) in immunocompromised mice. The interaction has also been observed in an endometrial carcinoma cell line. In contrast, no effect of ascorbic acid (at plasma concentrations commensurate with human supplemental intake) on bortezomib activity was found in immunocompromised mice bearing CWR22 human prostate xenograft tumors. In light of the fact that vitamin C may protect normal cells from bortezomib toxicity, more studies are needed to further clarify the clinical significance of these findings.

MANAGEMENT: Until more data are available, it may be advisable to avoid taking supplements containing ascorbic acid during bortezomib therapy, or at least on bortezomib treatment days.