Metabolic Detoxication, Phase I

**Definition:** Functionalization of exogenous substances to prepare them for conjugation in PHASE II DETOXIFICATION. Phase I enzymes include CYTOCHROME P450 enzymes and some OXIDOREDUCTASES. Excess induction of phase I over phase II detoxification leads to higher levels of FREE RADICALS that can induce CANCER and other cell damage. Induction or antagonism of phase I detoxication is the basis of a number of DRUG INTERACTIONS.

**Tree numbers:** - G03.171.450.500 - G03.787.225.450.500 - G07.690.725.225.450.500

**Synonyms:** - Metabolic Detoxification, Phase I - Metabolic Detoxication, Oxidative - Phase I Detoxification