Comparative Pharmacology
Head-to-head clinical analysis: NORDETTE 21 versus NORINYL 1 50 21 DAY.
Peer-Reviewed Evidence
Head-to-head clinical analysis: NORDETTE 21 versus NORINYL 1 50 21 DAY.
NORDETTE-21 vs NORINYL 1+50 21-DAY
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination oral contraceptive containing ethinyl estradiol and levonorgestrel. Inhibits ovulation by suppressing gonadotropin release, increases viscosity of cervical mucus to prevent sperm penetration, and alters endometrial lining to reduce implantation likelihood.
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 (0.15 mg levonorgestrel, 0.03 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days off.
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
Ethinylestradiol: 13 ± 7 hours (terminal), clinically relevant for once-daily dosing; Levonorgestrel: 24 ± 6 hours (terminal), supporting steady-state after ~5 days
Norethindrone: 5-8 hours; Ethinyl estradiol: 7-15 hours; steady-state reached within 5-7 days
Renal: ~50% (as glucuronide and sulfate conjugates); Fecal: ~40% (enterohepatic recirculation); Biliary: <10%
Renal (40% as metabolites), fecal (50% as metabolites), <1% unchanged
Category C
Category C
Combined Oral Contraceptive
Combined Oral Contraceptive