[Identification of chlorzoxazone metabolites in human urine (author's transl)]

Besides 6-hydroxychlorzoxazon II, the main metabolite of 5-chlorobenzoxazolin-2-one (chlorzoxazone I, Paraflex) two other compounds were found to be metabolites of chlorzoxazone: 5-chloro-2,4-dihydroxyacetanilide XXII is produced from 6-hydroxychlorzoxazone II by ring cleavage and acetylation of the nitrogen. More interesting is the formation of the 6-hydroxybenzoxazolone XX. This compound is formally produced by substitution of Cl for hydrogen and hydroxylation of a neighbour ring-carbon atom.