Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ENOVID vs ALYACEN 1/35
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Combination estrogen-progestin contraceptive; suppresses gonadotropins (LH, FSH) via negative feedback on hypothalamic-pituitary axis, inhibiting ovulation; increases viscosity of cervical mucus and alters endometrial lining to impair implantation.
Combination hormonal contraceptive: ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; norethindrone induces progestational effects including cervical mucus thickening and endometrial changes, inhibiting ovulation and sperm penetration.
Oral contraception,Treatment of endometriosis,Dysfunctional uterine bleeding,Postponement of menstruation
Prevention of pregnancy
Oral, 5 mg daily for 20 days starting on day 5 of menstrual cycle for ovulation inhibition; for endometriosis, 5 mg daily for 15 days increasing to 10 mg daily if breakthrough bleeding occurs.
One tablet (norethindrone 1 mg and ethinyl estradiol 35 mcg) orally once daily for 21 consecutive days, followed by 7 days of placebo or no tablets.
Norethynodrel: 5-12 hours; mestranol: 7-20 hours. Terminal half-life of ethinyl estradiol from mestranol conversion: 10-30 hours. Clinical context: steady-state achieved after 3-5 half-lives (3-5 days).
Norethindrone: 8-11 hours (terminal); ethinyl estradiol: 10-20 hours (terminal). The half-life supports once-daily dosing for oral contraceptive efficacy.
Hepatic via CYP3A4; norethynodrel is metabolized to norethindrone; mestranol is demethylated to ethinyl estradiol; metabolites undergo glucuronidation and sulfation.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Renal (30-50% as metabolites, <5% unchanged) and fecal (40-60% via bile, mostly as glucuronide conjugates).
Renal excretion of metabolites (primarily ethinyl estradiol and norethindrone conjugates) accounts for approximately 50-60% of elimination; fecal excretion accounts for 30-40%. Unchanged drug excretion is minimal (<5%).
Norethynodrel: 95-97% bound to albumin; mestranol: >95% bound to albumin and sex hormone-binding globulin (SHBG).
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
Norethynodrel: ~2.0 L/kg; mestranol: ~3.5 L/kg. High Vd indicates extensive tissue distribution.
Norethindrone: 3.8-4.5 L/kg; ethinyl estradiol: 2.0-4.0 L/kg. Large Vd indicates extensive tissue distribution.
Oral: 80-100% for norethynodrel; mestranol: 40-60% (first-pass metabolism to ethinyl estradiol).
Oral: Norethindrone ~64%, ethinyl estradiol ~38-48% (due to first-pass metabolism).
No specific dose adjustment guidelines; use with caution in severe renal impairment (GFR <30 m L/min) due to potential fluid retention.
No dose adjustment required for mild to moderate renal impairment. Contraindicated in severe renal impairment or acute renal failure due to potential fluid retention and electrolyte disturbances.
Contraindicated in severe hepatic impairment (Child-Pugh C); in mild to moderate impairment (Child-Pugh A or B), reduce dose by 50% or use alternative therapy.
Contraindicated in patients with hepatic impairment, including Child-Pugh class B or C, due to impaired metabolism of estrogen and progestin. Not recommended in patients with active liver disease or history of liver tumors.
Not recommended for use in pediatric patients for contraception; for endometriosis in adolescents, dose same as adult adjusted for weight (0.1-0.2 mg/kg/day norethynodrel equivalent, max 5 mg/day).
Not indicated for use before menarche. For postmenarchal adolescents, same dosing as adults. Safety and efficacy established for contraception; weight-based dosing not applicable.
Not indicated for contraception in postmenopausal women; if used for other indications, monitor for thromboembolic events and electrolyte disturbances; initiate at lowest effective dose (2.5 mg/day).
Not indicated for use after menopause due to lack of benefit and increased risks (e.g., cardiovascular, thromboembolic events). If used, monitor for fluid retention, hypertension, and glucose intolerance.
Cigarette smoking increases risk of serious cardiovascular events; contraindicated in women over 35 who smoke.
Cigarette smoking increases risk of serious cardiovascular events from combined oral contraceptives. Risk increases with age and heavy smoking (≥15 cigarettes/day). Women over 35 who smoke should not use this product.
Increased risk of thromboembolic disorders (stroke, MI, DVT, PE), hepatic neoplasia, gallbladder disease, hypertension, glucose intolerance, and depression. Discontinue if jaundice or visual disturbances occur.
Thrombotic disorders (e.g., DVT, PE, stroke, MI),Cerebrovascular disease,Hepatic neoplasia,Gallbladder disease,Hypertension,Carbohydrate and lipid effects,Ocular lesions,Hereditary angioedema,Chloasma,Menstrual irregularities,Pregnancy exclusion prior to initiation
Thrombophlebitis or thromboembolic disorders, cerebrovascular or coronary artery disease, known or suspected breast carcinoma, undiagnosed abnormal genital bleeding, pregnancy, known or suspected estrogen-dependent neoplasia, impaired liver function, history of cholestatic jaundice of pregnancy, heavy smoking (>15 cigarettes/day) in women over 35.
Venous or arterial thrombotic/thromboembolic disease (current or history),Cerebrovascular disease,Coronary artery disease,Known or suspected breast cancer,Endometrial or other estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Cholestatic jaundice of pregnancy or jaundice with prior pill use,Hepatic adenoma or carcinoma,Known or suspected pregnancy,Hypersensitivity to any component,Smoking in women over 35
No significant food interactions. Grapefruit juice may increase estrogen levels; avoid large amounts. Maintain consistent dietary habits to avoid fluctuations in hormone levels.
No significant food interactions. Grapefruit juice may increase estrogen levels, but clinically not a concern. Avoid excessive alcohol, which may impair liver function and increase estrogen exposure. Maintain a healthy diet, as weight gain is possible.
First trimester: Risk of fetal cardiovascular defects, neural tube defects, and cleft lip/palate. Second and third trimesters: Possible feminization of male fetuses (hypospadias) and clitoral enlargement in females. Postnatal: Vaginal adenosis and clear cell adenocarcinoma of the vagina/cervix in females exposed in utero.
Pregnancy category X. Use of ALYACEN 1/35 (norethindrone/ethinyl estradiol) is contraindicated during pregnancy. First trimester: Increased risk of congenital anomalies, including cardiovascular defects and limb reduction defects. Second/third trimesters: Potential for urogenital abnormalities and feminization of male fetus. Exposure is associated with subsequent development of clear cell adenocarcinoma of vagina/cervix in female offspring (DES-related).
Excretion into breast milk occurs; M/P ratio not established. Avoid use during breastfeeding due to potential hormonal effects on infant. Alternative contraception recommended.
Small amounts of contraceptive steroids and/or metabolites have been identified in breast milk. M/P ratio: Not specifically determined for this combination; ethinyl estradiol M/P ratio ~0.02-0.04. Use may reduce milk production and quality. Breastfeeding not recommended during use. Alternative contraception advised.
Contraindicated in pregnancy. No dosing adjustments applicable; if inadvertent exposure occurs, immediately discontinue the drug and provide counseling regarding risks.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
Monitor for thromboembolic events, especially in women over 35 who smoke. Use lowest effective dose for shortest duration. Discontinue 4 weeks before elective surgery to reduce clotting risk. Not recommended for contraception due to high estrogen dose.
ALYACEN 1/35 is a combination oral contraceptive containing ethinyl estradiol 35 mcg and norgestimate 1 mg. It is indicated for the prevention of pregnancy and for the treatment of moderate acne vulgaris in females ≥15 years of age who desire an oral contraceptive. Monitor for thromboembolic events, especially in smokers over 35 or those with migraine with aura. Use with caution in patients with liver impairment or history of cholestatic jaundice. The pill-free interval should not exceed 7 days; missed pills increase ovulation risk. Consider non-hormonal backup if vomiting or diarrhea occurs within 4 hours of dosing.
Take at same time daily with food to reduce nausea.,Report symptoms of blood clots: chest pain, sudden shortness of breath, leg pain/swelling, severe headache, vision changes.,Do not use if pregnant or breastfeeding; seek alternative contraception.,Smoking increases risk of serious cardiovascular side effects.,Use backup contraception if vomiting occurs within 4 hours of dose.
Take one tablet daily at the same time each day; do not skip doses.,Use an additional non-hormonal contraceptive (e.g., condoms) if you miss a pill, have vomiting, or diarrhea.,Smoking while on this pill increases the risk of blood clots and stroke, especially if you are over 35.,Contact your healthcare provider immediately if you have chest pain, leg pain/swelling, sudden vision changes, or severe headache.,This medication does not protect against HIV or other sexually transmitted infections.,Store at room temperature, away from moisture and heat.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ENOVID vs ALYACEN 1/35, answered by our medical review team.
ENOVID is a Oral Contraceptive that works by Combination estrogen-progestin contraceptive; suppresses gonadotropins (LH, FSH) via negative feedback on hypothalamic-pituitary axis, inhibiting ovulation; increases viscosity of cervical mucus and alters endometrial lining to impair implantation.. ALYACEN 1/35 is a Oral Contraceptive that works by Combination hormonal contraceptive: ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; norethindrone induces progestational effects including cervical mucus thickening and endometrial changes, inhibiting ovulation and sperm penetration.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ENOVID and ALYACEN 1/35 depend on the specific clinical indication. These are both Oral Contraceptive agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ENOVID is: Oral, 5 mg daily for 20 days starting on day 5 of menstrual cycle for ovulation inhibition; for endometriosis, 5 mg daily for 15 days increasing to 10 mg daily if breakthrough bleeding occurs.. The standard adult dose of ALYACEN 1/35 is: One tablet (norethindrone 1 mg and ethinyl estradiol 35 mcg) orally once daily for 21 consecutive days, followed by 7 days of placebo or no tablets.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ENOVID and ALYACEN 1/35 in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ENOVID is classified as Category C. First trimester: Risk of fetal cardiovascular defects, neural tube defects, and cleft lip/palate. Second and third trimesters: Possible feminization of male fetuses (hypospadias) a. ALYACEN 1/35 is classified as Category C. Pregnancy category X. Use of ALYACEN 1/35 (norethindrone/ethinyl estradiol) is contraindicated during pregnancy. First trimester: Increased risk of congenital anomalies, including . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.