Procarbazine
Procarbazine is only found in individuals that have used or taken this drug. It is an antineoplastic agent used primarily in combination with mechlorethamine, vincristine, and prednisone (the MOPP protocol) in the treatment of Hodgkin's disease. The precise mode of cytotoxic action of procarbazine has not been clearly defined. There is evidence that the drug may act by inhibition of protein, RNA and DNA synthesis. Studies have suggested that procarbazine may inhibit transmethylation of methyl groups of methionine into t-RNA. The absence of functional t-RNA could cause the cessation of protein synthesis and consequently DNA and RNA synthesis. In addition, procarbazine may directly damage DNA. Hydrogen peroxide, formed during the auto-oxidation of the drug, may attack protein sulfhydryl groups contained in residual protein which is tightly bound to DNA.