Comparative Pharmacology
Head-to-head clinical analysis: NORCEPT E 1 35 21 versus NORINYL 1 50 21 DAY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: NORCEPT E 1 35 21 versus NORINYL 1 50 21 DAY.
NORCEPT-E 1/35 21 vs NORINYL 1+50 21-DAY
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination oral contraceptive: estrogen (ethinyl estradiol) suppresses gonadotropin secretion, preventing ovulation; progestin (norethindrone) alters cervical mucus, endometrial lining, and inhibits sperm penetration.
Norinyl 1+50 21-Day contains norethindrone (a progestin) and mestranol (an estrogen). Mestranol is converted to ethinyl estradiol, which provides negative feedback on gonadotropin release, inhibiting ovulation. Norethindrone suppresses gonadotropins and alters cervical mucus and endometrial lining to prevent implantation.
One tablet (norethindrone 1 mg + ethinyl estradiol 35 mcg) orally once daily for 21 days, followed by 7 days of placebo or no tablets. Repeat cycle continuously.
One tablet (1 mg norethindrone + 0.05 mg mestranol) orally once daily for 21 days, followed by 7 placebo tablets. Start on day 1 of menstrual cycle or first Sunday after onset.
None Documented
None Documented
Ethinyl estradiol: terminal half-life approximately 17 hours (range 13-27 hours), consistent with once-daily dosing; norethindrone: terminal half-life approximately 7.6 hours (range 5-12 hours), permitting steady-state within 5 days.
Norethindrone: 5-8 hours; Ethinyl estradiol: 7-15 hours; steady-state reached within 5-7 days
Renal: 50-60% as metabolites (primarily ethinyl estradiol glucuronide and norethindrone metabolites); fecal: 20-30% via biliary elimination; unchanged drug: <5%.
Renal (40% as metabolites), fecal (50% as metabolites), <1% unchanged
Category C
Category C
Combined Oral Contraceptive
Combined Oral Contraceptive