CYTOTOXIC DRUG

any drug poisonous to cells. Such drugs may disturb fundamental mechanisms involving cell growth, differentiation, and function and the activity of the chromosomes (bodies containing the genes) at some stage preceding their duplication. There is a great difference in the susceptibility of various types of cells and in the lethal capacities of the drugs used. The cells that are most susceptible to inhibition and damage by cytotoxic drugs appear to be rapidly proliferating ones, such as those in the blood and lymph-forming system, the reproductive and other epithelial tissue (e.g., intestinal mucosa), and neoplastic (cancerous) tissue. The immune response is also suppressed by various cytotoxic drugs. Cytotoxic drugs such as cyclophosphamide, methotrexate, and mercaptopurine (6-purinethiol) are useful in the management of certain cancers (especially in leukemias), in the suppression of immune responses following tissue or organ transplants, and in treating certain allergic disorders.