Comparative Pharmacology
Head-to-head clinical analysis: KELNOR 1 50 versus NORTREL 1 35 21.
Peer-Reviewed Evidence
Head-to-head clinical analysis: KELNOR 1 50 versus NORTREL 1 35 21.
KELNOR 1/50 vs NORTREL 1/35-21
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.
Combination of ethinyl estradiol (estrogen) and norethindrone (progestin) suppresses gonadotropin (FSH and LH) release from the pituitary, inhibiting ovulation, altering cervical mucus to impede sperm penetration, and inducing endometrial changes that reduce implantation likelihood.
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.
One tablet orally once daily for 21 days, followed by 7 days off, then repeat.
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: 5-14 hours; Ethinyl estradiol: 17-24 hours. Steady-state achieved after 10 days.
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 50-60% as metabolites, fecal 40-50% as conjugates, <1% unchanged
Category C
Category C
Oral Contraceptive
Oral Contraceptive