In order for drugs to be eliminated from the body, the body has to make them water soluble. Only when after drugs are made soluble in the blood can they be filtered out of the body by the kidneys and excreted into urine. The liver plays the major role in converting lipophilic, nonpolar molecules to more polar, water soluble forms. It does this through a series of enzymatic reactions. Drug molecules can be modified by either phase I or phase II reactions. These reactions are carried out by several important classes of enzymes.
- Phase I reactions alter a drug's chemical structure by oxidation, reduction, or hydrolysis.
- Phase ll reactions conjugate drugs with other molecules to create products that are water soluble.
