Comparative Pharmacology
Head-to-head clinical analysis: CYCLAFEM 0 5 35 versus NORLESTRIN 28 1 50.
Peer-Reviewed Evidence
Head-to-head clinical analysis: CYCLAFEM 0 5 35 versus NORLESTRIN 28 1 50.
CYCLAFEM 0.5/35 vs NORLESTRIN 28 1/50
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination oral contraceptive containing norethindrone (progestin) and ethinyl estradiol (estrogen). Inhibits gonadotropin release, suppressing ovulation. Increases cervical mucus viscosity and alters endometrium, reducing sperm penetration and implantation.
Combination estrogen-progestin oral contraceptive; suppresses gonadotropin release via negative feedback on pituitary, inhibits ovulation, thickens cervical mucus, alters endometrial receptivity.
One tablet (0.5 mg norethindrone/35 mcg ethinyl estradiol) orally once daily for 21 days, followed by 7 placebo days (or no tablets) per cycle.
One tablet orally once daily, each containing norethindrone 1 mg and ethinyl estradiol 50 mcg.
None Documented
None Documented
Terminal elimination half-life of norethindrone is 5-14 hours (mean 7.6 hours); ethinyl estradiol half-life is 7-20 hours (mean ~13 hours). Steady-state is achieved within 5-7 days.
Norethindrone: 8 hours; ethinyl estradiol: 12-15 hours; steady state achieved within 5-10 days.
Renal excretion accounts for approximately 50-60% of the dose (as metabolites), with 30-40% excreted in feces via biliary elimination. Unchanged drug is minimal in urine.
Norethindrone: 40% renal, 60% fecal; ethinyl estradiol: 40% renal, 60% fecal.
Category C
Category C
Oral Contraceptive
Oral Contraceptive