Fipronil (FIP) is a broad-spectrum insecticide belonging to the phenylpyrazole group. The main metabolites of FIP are FIP sulfone, FIP sulfide, FIP amide, and FIP desulfinyl. FIP metabolizes into FIP sulfone through the oxidation of the sulfinyl group, into FIP sulfide by reducing the sulfinyl group, and into FIP amide through the hydrolysis of the cyano group. FIP desulfinyl is formed through a photochemical reaction (under UV light). FIP sulfone, FIP sulfide, and FIP desulfinyl are highly toxic metabolites.