Definition Barbiturates (except for the less-soluble phenobarbital) are mainly metabolized by the liver into inactive, water-soluble compounds by oxidation and then are renally excreted or conjugated to glucuronic acid and excreted in bile. The most significant aspect of the metabolism of barbiturates (e.g., phenobarbital, thiopental, methohexital) is their effect on the hepatic microsomal enzyme system […]