Studier, hvor der er anvendt humant levermateriale og rekombinante humane enzymer, indikerer, at CYP3A4 er det eneste P- 450 isoenzym, der er involveret i oxidation af fulvestrant, hvor veje, der ikke involverer P- 450, dog synes mere fremtrædende in vivo.
Studies using human liver preparations and recombinant human enzymes indicate that CYP3A4 is the only P450 isoenzyme involved in the oxidation of fulvestrant; however, non-P450 routes appear to be more predominant in vivo.