5-hydroxytienilic acid

Tienilic acid is oxidized in the liver by CYP monooxygenase to 5-hydroxytienilic acid, which is the major urinary metabolite (about 50% in human). In humans, the bioactivation of tienilic acid depends on CYP2C9. This isoform is one of the major forms of CYP in the human liver. This oxidation occurs through an electrophilic intermediate capable of alkylating very specifically the leading... 

The metabolism of tienilic acid provides further evidence. Tienilic acid, a diuretic drug that is involved in the appearance of rare cases of immunoallergic hepatitis, leads to 5-hydroxytienilic acid as a major metabolite in vivo and in vitro (Scheme 14) [4, 23, 24]. 

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