Stages of Metabolism
The liver hepatocytes contain all the necessary enzymes for the metabolism of drugs. The main enzymes involved in metabolism belong to the cytochrome P450 group. These are a large family of related enzymes housed in the smooth endoplasmic reticulum of the cell.
Metabolism is often divided into two phases of biochemical reaction - phase 1 and phase 2. Some drugs may undergo just phase 1 or just phase 2 metabolism, but more often, the drug will undergo phase 1 and then phase 2 sequentially.