Carmustine, also known as BCNU, is a cytostatically active drug (molecular formula C5H9Cl2N3O2) from the group of nitrosoureas, which is used in the treatment of certain severe, advanced tumour diseases. Carmustine, like the nitrogen-lost derivatives and the related nitrosourea lomustine, contains chloroethyl residues and additionally a highly reactive nitroso group.
The carmustine molecules decompose spontaneously and release the alkylating ethyl carbonium ion, which causes cross-linking of the DNA by alkylation of guanine and cytosine.
In addition, isocyanates are formed, which also inhibit DNA repair by combining with the DNA polymerase. Carmustin and lomustin have a phase-independent effect, i.e. they also act on resting cells.