Comparative Pharmacology
Head-to-head clinical analysis: NORETHIN 1 35E 28 versus NORINYL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: NORETHIN 1 35E 28 versus NORINYL.
NORETHIN 1/35E-28 vs NORINYL
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination estrogen-progestin oral contraceptive. Ethinyl estradiol suppresses FSH and LH, preventing ovulation. Norethindrone alters cervical mucus and endometrial lining, inhibiting sperm penetration and implantation.
Combination of norethindrone (progestin) and ethinyl estradiol (estrogen) provides contraception by inhibiting gonadotropin secretion via negative feedback on the hypothalamic-pituitary-ovarian axis, suppressing ovulation, increasing cervical mucus viscosity, and altering endometrial receptivity.
One tablet orally once daily for 28 days (21 active tablets containing norethindrone 1 mg and ethinyl estradiol 35 mcg, followed by 7 inert tablets).
One tablet (norethindrone 1 mg/ethinyl estradiol 0.035 mg) orally once daily for 21 days, followed by 7 placebo tablets. For first cycle, start on first Sunday after menstruation begins or on day 1 of menstrual cycle.
None Documented
None Documented
Norethindrone: terminal elimination half-life approximately 8-11 hours. Ethinyl estradiol: terminal elimination half-life approximately 10-20 hours (mean ~13 hours). Clinical context: Steady-state achieved within 5 days; once-daily dosing maintains therapeutic levels.
Terminal half-life: norethindrone 7-8 hours, ethinyl estradiol 13-27 hours; clinical context: steady-state achieved in 3-5 half-lives
Norethindrone is excreted primarily in urine as glucuronide and sulfate conjugates, with about 50-60% excreted renally; approximately 20-30% is excreted in feces via biliary elimination. Ethinyl estradiol is excreted in urine (40-60%) and feces (20-40%) after enterohepatic recirculation.
Renal: ~60% as metabolites, biliary/fecal: ~40% as glucuronide conjugates
Category C
Category C
Combined Oral Contraceptive
Combined Oral Contraceptive