Comparative Pharmacology
Head-to-head clinical analysis: KELNOR 1 50 versus NORTREL 0 5 35 28.
Peer-Reviewed Evidence
Head-to-head clinical analysis: KELNOR 1 50 versus NORTREL 0 5 35 28.
KELNOR 1/50 vs NORTREL 0.5/35-28
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination hormonal contraceptive: ethinyl estradiol provides estrogenic activity, suppressing gonadotropin release; norethindrone acetate provides progestational activity, inhibiting ovulation and causing cervical mucus thickening.
Norethindrone and ethinyl estradiol are a combination hormonal contraceptive. Norethindrone suppresses gonadotropin release (FSH and LH) from the pituitary, inhibiting ovulation. Ethinyl estradiol stabilizes the endometrium and enhances the contraceptive effect by inhibiting gonadotropin secretion.
One tablet (norethindrone 1 mg/ethinyl estradiol 50 mcg) orally once daily, taken at the same time each day for 21 days, followed by 7 days of placebo.
1 tablet orally once daily for 28 days (21 active tablets containing 0.5 mg norethindrone and 35 mcg ethinyl estradiol, followed by 7 placebo tablets).
None Documented
None Documented
Ethinyl estradiol: biphasic, terminal half-life 13-27 hours (mean ~17 h); norethindrone: monoexponential, half-life 5-14 hours (mean ~8 h). Steady-state achieved after 3-5 days. Accumulation may occur in patients with hepatic impairment.
Norethindrone: 7.2-9.2 hours; Ethinyl estradiol: 13-27 hours. Clinical context: Steady state reached in 5-7 days; half-life supports once-daily dosing.
Renal: ~50% (as metabolites, primarily ethinyl estradiol glucuronide and sulfate conjugates; norethindrone metabolites). Fecal: ~35% (biliary excretion of conjugates followed by hydrolysis and elimination). Unchanged drug: <5%.
Renal: ~40% as metabolites; Biliary/Fecal: ~60% as metabolites; <5% unchanged.
Category C
Category C
Oral Contraceptive
Oral Contraceptive