The liver plays a major role in converting lipophilic, nonpolar molecules (including drugs) to more polar, water-soluble forms through a series of enzymatic reactions. Drug molecules can be modified by either phase I or phase ll reactions. These reactions are carried out by several important classes of enzymes.
- Phase I reactions alter chemical structure by oxidation, reduction, or hydrolysis.
- Phase ll reactions conjugate drugs to create products that are water-soluble.