Comparative Pharmacology
Head-to-head clinical analysis: ENOVID E 21 versus NORTREL 1 35 21.
Peer-Reviewed Evidence
Head-to-head clinical analysis: ENOVID E 21 versus NORTREL 1 35 21.
ENOVID-E 21 vs NORTREL 1/35-21
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Norethindrone is a progestin that suppresses gonadotropin release, inhibiting ovulation; mestranol is an estrogen that stabilizes endometrium and provides cycle control.
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 (norethynodrel 2.5 mg, mestranol 0.1 mg) orally once daily for 21 consecutive days, followed by 7 days without medication. Repeat cycle.
One tablet orally once daily for 21 days, followed by 7 days off, then repeat.
None Documented
None Documented
Terminal elimination half-life: 27–36 hours (mean 30.8 h). Steady-state reached after 5–7 days. Clinical context: allows once-daily dosing with stable estrogenic effect.
Norethindrone: 5-14 hours; Ethinyl estradiol: 17-24 hours. Steady-state achieved after 10 days.
73% renal (45% as unchanged norethindrone, 20% as conjugates, 8% as other metabolites), 27% fecal via bile. Enterohepatic recirculation accounts for 15% of total clearance.
Renal 50-60% as metabolites, fecal 40-50% as conjugates, <1% unchanged
Category C
Category C
Oral Contraceptive
Oral Contraceptive