So named because they alkylate or chemically react with certain biochemical entities, particularly those concerned with the synthesis of NUCLEIC ACID. Alkylation is the substitution of an organic grouping in place of another grouping in a molecule.

Alkylating agents are important because they interfere with the growth and reproduction of cells, disrupting their replication. This CYTOTOXIC property is used to retard the division and growth of cancer cells, and alkylating drugs are widely used in CHEMOTHERAPY of malignant tumours – often in conjunction with surgery and sometimes with radiotherapy. Unfortunately, troublesome side-effects occur, such as: damage to veins when the drug is given intravenously, with resultant leakage into adjacent tissues; impaired kidney function due to the formation of URIC ACID crystals; nausea and vomiting; ALOPECIA (hair loss); suppression of BONE MARROW activity and of the production of blood cells; and adverse effects on reproductive function, including TERATOGENESIS. Indeed, cytotoxic drugs must not be given in pregnancy, especially during the first three months. Among the dozen or so alkylating drugs in use are, CHLORAMBUCIL, MELPHALAN, BUSULFAN and THIOTEPA.