Comparative Pharmacology
Head-to-head clinical analysis: NORINYL 1 35 28 DAY versus NORINYL 1 50 21 DAY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: NORINYL 1 35 28 DAY versus NORINYL 1 50 21 DAY.
NORINYL 1+35 28-DAY vs NORINYL 1+50 21-DAY
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Norethindrone is a progestogen that suppresses gonadotropin release, inhibiting ovulation; ethinyl estradiol is an estrogen that provides negative feedback on the hypothalamic-pituitary-ovarian axis, further suppressing ovulation and altering cervical mucus and endometrial thickness.
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 orally once daily for 28 consecutive days (21 active tablets followed by 7 inert tablets).
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
Norethindrone: 7-8 hours (terminal half-life); steady state achieved after 5 days. Ethinyl estradiol: biphasic with terminal half-life of 13-27 hours (mean ~17 hours). Clinical context: dosing interval of 24 hours allows stable hormone levels after first cycle.
Norethindrone: 5-8 hours; Ethinyl estradiol: 7-15 hours; steady-state reached within 5-7 days
Renal: 50-60% (conjugates and metabolites), Fecal: 30-40% (biliary elimination of norethindrone and ethinyl estradiol conjugates); total clearance ~4-6 mL/min/kg.
Renal (40% as metabolites), fecal (50% as metabolites), <1% unchanged
Category C
Category C
Combined Oral Contraceptive
Combined Oral Contraceptive