Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
N.E.E. 1/35 28 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 oral contraceptive; ethinyl estradiol and norethindrone suppress gonadotropin (FSH and LH) release, preventing ovulation. Also cause cervical mucus thickening and endometrial changes.
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.
Prevention of pregnancy
Prevention of pregnancy
One tablet orally once daily for 28 days; each tablet contains norethindrone 1 mg and ethinyl estradiol 35 mcg.
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.
Ethinyl estradiol: ~15-19 hours (linear pharmacokinetics); Norethindrone: ~7-9 hours (terminal half-life; steady-state achieved within 5-7 days)
Norethindrone: 8-11 hours (terminal); ethinyl estradiol: 10-20 hours (terminal). The half-life supports once-daily dosing for oral contraceptive efficacy.
Ethinyl estradiol: primarily metabolized by CYP3A4; undergoes sulfation and glucuronidation. Norethindrone: metabolized in the liver via reduction and glucuronidation.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Renal: ~50-60% (metabolites, primarily glucuronide conjugates); Fecal: ~30-40% (biliary excretion of metabolites); Unchanged drug: <5%
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%).
Ethinyl estradiol: ~97-98% bound primarily to albumin; Norethindrone: ~96-97% bound to albumin and SHBG
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
Ethinyl estradiol: ~2.5-4 L/kg; Norethindrone: ~3.5-5 L/kg; reflects 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: Ethinyl estradiol ~40-50% (first-pass metabolism); Norethindrone ~65-70% (first-pass metabolism)
Oral: Norethindrone ~64%, ethinyl estradiol ~38-48% (due to first-pass metabolism).
No specific dose adjustment recommended; use with caution in patients with renal impairment.
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 patients with acute hepatitis, severe cirrhosis, or liver tumors (benign or malignant). For Child-Pugh Class C: contraindicated. For Child-Pugh Class A or B: use with caution and monitor liver function.
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.
Postmenarchal adolescents: same as adult dosing (one tablet orally once daily). Safety and efficacy established for use after menarche.
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 postmenopausal women due to lack of need for contraception and potential increased risk of thromboembolism and cardiovascular events.
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 from combination oral contraceptives. Risk increases with age (>35 years) and heavy smoking (>15 cigarettes/day). Women over 35 who smoke should not use this product.
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.
Thrombotic disorders (venous thromboembolism, stroke, MI),Hepatic neoplasia,Gallbladder disease,Hypertension,Carbohydrate/lipid effects,Ocular lesions (retinal thrombosis),Carcinoma (breast, cervical),Hereditary angioedema,Chloasma,Pregnancy (discontinue if pregnant),Lactation (may reduce milk production)
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,Endometrial carcinoma or other estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Pregnancy,Hepatic adenoma or carcinoma,Active liver disease or impaired liver function,Known hypersensitivity to any component,Smoking if age >35 years
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 slightly increase ethinyl estradiol levels but no dose adjustment needed. High-fat meals do not affect absorption.
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: No increased risk of major birth defects from combined oral contraceptives based on population data; however, inadvertent use is not recommended. Second/third trimester: Avoid use due to potential adverse fetal effects including hormonal disruption. Category X for pregnancy contraindication.
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).
Excreted in breast milk in small amounts (estrogen: M/P ratio ~0.5; progestin data limited). May reduce milk production and quality. Not recommended for nursing mothers. Alternative contraception advised.
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.
No dose adjustments applicable as the drug is contraindicated in pregnancy. Pharmacokinetic changes (e.g., increased clearance of hormones) occur but are not managed with dose changes due to risk.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
N. E. E. 1/35 28 is a monophasic combined oral contraceptive containing norethindrone and ethinyl estradiol. Monitor for thromboembolic events, especially in smokers over 35. Efficacy may be reduced with hepatic enzyme inducers. Bleeding irregularities are common in the first 3 cycles.
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 one tablet daily at the same time, in the order listed on the pack.,Missed pill instructions: if one pill is missed, take it as soon as remembered; if two or more are missed, use back-up contraception for 7 days.,Common side effects include nausea, breast tenderness, and breakthrough bleeding.,Seek immediate medical attention for symptoms of blood clots: leg pain/swelling, sudden chest pain, shortness of breath, or severe headache.,Do not smoke while taking this medication, as smoking increases the risk of serious cardiovascular side effects.,Inform your healthcare provider if you are breastfeeding or have a history of migraines, hypertension, or liver disease.
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 N.E.E. 1/35 28 vs ALYACEN 1/35, answered by our medical review team.
N.E.E. 1/35 28 is a Oral Contraceptive that works by Combination oral contraceptive; ethinyl estradiol and norethindrone suppress gonadotropin (FSH and LH) release, preventing ovulation. Also cause cervical mucus thickening and endometrial changes.. 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 N.E.E. 1/35 28 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 N.E.E. 1/35 28 is: One tablet orally once daily for 28 days; each tablet contains norethindrone 1 mg and ethinyl estradiol 35 mcg.. 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 N.E.E. 1/35 28 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. N.E.E. 1/35 28 is classified as Category C. First trimester: No increased risk of major birth defects from combined oral contraceptives based on population data; however, inadvertent use is not recommended. Second/third trim. 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.