Comparative Pharmacology
Head-to-head clinical analysis: CYCLAFEM 1 35 versus LESSINA 21.
Peer-Reviewed Evidence
Head-to-head clinical analysis: CYCLAFEM 1 35 versus LESSINA 21.
CYCLAFEM 1/35 vs LESSINA-21
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Combination oral contraceptive containing ethinyl estradiol and norethindrone. Suppresses gonadotropin (FSH, LH) secretion via estrogen and progestin negative feedback, inhibiting ovulation. Progestin alters cervical mucus (sperm penetration) and endometrial receptivity.
Combination oral contraceptive containing ethinyl estradiol and levonorgestrel. Suppresses gonadotropin release (FSH, LH) from pituitary, inhibiting ovulation. Causes cervical mucus thickening and endometrial alterations, impeding sperm penetration and implantation.
One tablet orally once daily. Each tablet contains 1 mg norethindrone and 0.035 mg ethinyl estradiol. Administer daily for 21 days followed by 7 days of placebo or no tablet.
One tablet (0.1 mg levonorgestrel, 0.02 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days placebo or no tablets.
None Documented
None Documented
Half-life of norethindrone is 5-14 hours; ethinyl estradiol is 10-20 hours. Steady state reached after 5-7 days.
17-21 hours (terminal elimination half-life; clinical significance: allows once-daily dosing, but missed doses increase risk of ovulation)
Renal 40-60% as glucuronide and sulfate conjugates, biliary/fecal 20-40%.
Renal (70% as unchanged drug and metabolites), fecal (30% as metabolites)
Category C
Category C
Oral Contraceptive
Oral Contraceptive