Like all combined hormonal contraceptives, Ortho Evra / Evra works primarily by preventing ovulation. A secondary mechanism of action is inhibition of sperm penetration by changes in the cervical mucus. Hormonal contraceptives also have effects on the endometrium that theoretically could affect implantation; however, no scientific evidence indicates that prevention of implantation actually results from their use.[7]
The 20 cm² Ortho Evra contraceptive patch contains 750 µg ethinyl estradiol (an estrogen) and 6000 µg norelgestromin (a progestin).[8] The 20 cm² Evra contraceptive patch contains 600 µg ethinyl estradiol and 6000 µg norelgestromin.[9] The Ortho Evra contraceptive patch and the Evra contraceptive patch are both intended to gradually release into the systemic circulation approximately 20 µg/day of ethinyl estradiol and 150 µg/day of norelgestromin.[8][9]