A review of the pharmacodynamic effect of chemo-herbal drug combinations therapy for cancer treatment

There is mounting evidence that cancer patients co-administer herbal drugs with chemotherapy, however, information on the pharmacodynamic (PD) effects of such combination therapy is scarce. Natural products including crude extracts, herbal formulas, and bioactive compounds from plants hold great potential to prevent and treat cancers. More importantly, some herbal drugs can reduce the incidence of chemotherapy-induced toxicity including oral mucositis, gastrointestinal toxicity, hepatotoxicity etc. This review focuses on the effectiveness of some herbal products as adjuvant therapy and describes the possible mechanisms of chemo-herbal drug PD interactions in enhancing the efficacy/ or reducing the side effects of chemotherapy. We also highlighted recent advances in preclinical in vitro and in vivo studies to establish the effectiveness of herbal medicine to enhance efficacy or counteract chemotherapy-induced side effects. In addition, we draw particular attention to the synergistic effects of chemo-herbal drug combination therapy to prevent and treat cancers using evidence from clinical trials. We concluded that herbal drugs hold great potential as adjuvant therapy for the prevention and treatment of chemotherapy-induced side effects. It is important to also highlight that the clinical evidence on chemo-herbal drug combination therapy is limited. There is an urgent need for an in-depth PD evaluation including the safety pharmacology of chemo-herbal drug combination therapy as well as reliable evidence from multicentre clinical trials to establish the beneficial or negative effects of chemo-herbal drug combination therapy in the ongoing fight against cancer.