Phase I Detoxification:

A process in which the liver uses one of two major enzyme pathways to change a toxic substance into a less toxic substance that is easier for the body to excrete.

Phase II Detoxification:

A process in which the liver uses one of two major enzyme pathways to change a toxic substance into a less toxic substance that is easier for the body to excrete. In phase II detoxification, liver cells add a substance (such as cysteine, glycine, or a sulfur molecule) to a toxic chemical or drug, to make it less harmful.