Toxication, toxification or toxicity exaltation is the conversion of a chemical compound into a more toxic form in living organisms or in substrates such as soil or water. The conversion can be caused by enzymatic metabolism in the organisms, as well as by abiotic chemical reactions. While the parent drug is usually less active, both the parent drug and its metabolite can be chemically active and cause toxicity, leading to mutagenesis, teratogenesis, and carcinogenesis.[1][2] Different classes of enzymes, such as P450 monooxygenases, epoxide hydrolase, or acetyltransferases can catalyze the process in the cell, mostly in the liver.[2]
Parent non-toxic chemicals are generally referred to as protoxins. While toxication is generally undesirable, in certain cases it is required for the in vivo conversion of a prodrug to a metabolite with desired pharmacological or toxicological activity. Codeine is an example of a prodrug, metabolized in the body to the active compounds morphine and codeine-6-glucuronide.