The occurrence of 3-hydroxy-phenprobamate, a new metabolite of phenprobamate, in dogs and humans.

3-Hydroxy-phenprobamate has been isolated from the urine of dogs and humans following oral administration of phenprobamate. The structure of this new metabolite was determined by analysis of its spectral data and corroborated by an unequivocal synthesis. The relative concentration of this substance, as well as other neutral metabolites occurring in the urine, either in the free form or as the glucuronide conjugates, is presented for both species. The presence of 3-hydroxy-phenprobamate in human plasma, and its interference with phenprobamate plasma level analysis by a previously described colorimetric method, is discussed