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Definition of Cytotoxic
Medically reviewed by Min Clinic Staff | Updated: January 2026
Cytotoxic: Toxic to cells, cell-toxic, cell-killing. Any agent or process that kills cells. Chemotherapy and radiotherapy are forms of cytotoxic therapy. They kill cells.
The prefix cyto- denotes a cell. It comes from the Greek kytos meaning hollow, as a cell or container. Toxic is from the Greek toxikon = arrow poison.