Xenobiotic: a "foreign" compound which may be a drug or environmentally distributed chemical.

Detoxification: decreased activity following metabolism or biotransformation (note that metabolism does not always result in decreased activity).

Metabolism: often used to refer exclusively to normal anabolic and catabolic reactions of the body (protein, fat, carbohydrate, nucleic acids) but can refer to the chemical transformation of xenobiotics.

Biotransformation: the chemical transformation of xenobiotics.