Sulfates are the foremost circulating conjugates of ethinyl estradiol and glucuronides predominate in urine. The first oxidative metabolite is 2-hydroxy ethinyl estradiol, formed from the CYP3A4 isoform of cytochrome P450. Portion of the 1st-move metabolism of ethinyl estradiol is believed to occur in gastrointestinal mucosa. Ethinyl estradiol may