Comparative Pharmacology
Head-to-head clinical analysis: LOESTRIN 21 1 5 30 versus NORINYL 1 50 21 DAY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: LOESTRIN 21 1 5 30 versus NORINYL 1 50 21 DAY.
LOESTRIN 21 1.5/30 vs NORINYL 1+50 21-DAY
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination estrogen-progestin contraceptive: suppresses gonadotropin release, inhibiting ovulation; increases viscosity of cervical mucus, impeding sperm penetration; alters endometrial morphology.
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 acetate 1.5 mg/ethinyl estradiol 30 mcg) orally once daily for 21 consecutive days, followed by 7 days off therapy.
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: ~12-14 h; Norethindrone: ~5-12 h. Steady-state achieved in ~5-10 days.
Norethindrone: 5-8 hours; Ethinyl estradiol: 7-15 hours; steady-state reached within 5-7 days
Primarily hepatic metabolism; ~40-60% renal, 20-30% biliary/fecal.
Renal (40% as metabolites), fecal (50% as metabolites), <1% unchanged
Category C
Category C
Combined Oral Contraceptive
Combined Oral Contraceptive