Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NORTREL 1/35-21 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 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.
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,Oral contraception
Prevention of pregnancy
One tablet orally once daily for 21 days, followed by 7 days off, then repeat.
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.
Norethindrone: 5-14 hours; Ethinyl estradiol: 17-24 hours. Steady-state achieved after 10 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 undergoes hepatic metabolism primarily via CYP3A4 hydroxylation and conjugation; norethindrone is metabolized primarily via reduction and sulfate/glucuronide conjugation.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Renal 50-60% as metabolites, fecal 40-50% as conjugates, <1% unchanged
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%).
Norethindrone: 80% bound to albumin and SHBG; Ethinyl estradiol: 98% bound to albumin and SHBG.
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
Norethindrone: 2-4 L/kg; Ethinyl estradiol: 3-5 L/kg. 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: Norethindrone ~65% (first-pass metabolism), Ethinyl estradiol ~40-50% (first-pass metabolism).
Oral: Norethindrone ~64%, ethinyl estradiol ~38-48% (due to first-pass metabolism).
No dose adjustment required for renal impairment; use with caution in severe 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 acute liver disease, hepatocellular carcinoma, or active hepatitis. In Child-Pugh A: no adjustment; Child-Pugh B or C: contraindicated.
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 indicated for use before menarche; after menarche, same as adult dosing.
Not indicated for use before menarche. For postmenarchal adolescents, same dosing as adults. Safety and efficacy established for contraception; weight-based dosing not applicable.
No specific dose adjustment; estrogen-containing contraceptives are generally not recommended after menopause.
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 hormonal contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day) and is significant in women over 35. 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, myocardial infarction) – discontinue if occur or suspected,Elevated risk of thromboembolic events in smokers, especially over 35,Increased risk of gallbladder disease,Hepatic neoplasia (benign and malignant) – discontinue if jaundice or liver function abnormalities develop,Elevated blood pressure – monitor regularly,Carbohydrate and lipid metabolism effects – monitor in diabetic or hyperlipidemic patients,Ocular lesions (retinal thrombosis) – discontinue if unexplained vision loss occurs,Headache – evaluate if new or worsening migraine patterns,Uterine bleeding irregularities – rule out pregnancy or pathology
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 (current or history),Cerebrovascular or coronary artery disease,Known or suspected breast carcinoma or estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Pregnancy (known or suspected),Hepatic adenoma or carcinoma (benign or malignant liver tumors),Jaundice or impaired liver function (active liver disease),Hypersensitivity to any component,Smoking in women over 35,Uncontrolled hypertension,Diabetes with vascular involvement,Migraine with focal neurological symptoms (if 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 specific food restrictions; however, grapefruit juice may increase estrogen levels; avoid excessive consumption. Maintain consistent dietary patterns to avoid gastrointestinal interference with 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.
Category X. First trimester: No increased risk of major birth defects observed in clinical studies, but postmarketing data are insufficient. Second and third trimesters: Use associated with fetal harm, including cardiovascular defects, limb defects, and masculinization of female fetuses. Avoid during pregnancy.
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; M/P ratio for estrogen is 0.2, for progestin is 0.3. No adverse effects reported in nursing infants. American Academy of Pediatrics considers use compatible with breastfeeding, but may reduce milk production and quality. Use only if clearly needed.
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 adjustment required; drug is contraindicated in pregnancy. If inadvertently used, discontinue immediately.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
Nortrel 1/35-21 is a monophasic combined oral contraceptive containing 1 mg norethindrone and 35 mcg ethinyl estradiol. Administer 21 active tablets followed by 7 placebo tablets. Advise patients to take at the same time daily. Missed doses increase pregnancy risk; use backup contraception if missed. Not recommended in patients with BMI > 35 due to increased failure risk. Contraindicated in smokers over 35 years old.
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 pill at the same time each day, starting on the first day of your menstrual period.,If you miss a dose, take it as soon as remembered, and use a backup method for 7 days.,Do not smoke while taking this medication, especially if over 35 years old.,Common side effects include nausea, breast tenderness, and breakthrough bleeding.,Inform your doctor if you have liver disease, blood clots, breast cancer, or high blood pressure.
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 NORTREL 1/35-21 vs ALYACEN 1/35, answered by our medical review team.
NORTREL 1/35-21 is a Oral Contraceptive that works by 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.. 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 NORTREL 1/35-21 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 NORTREL 1/35-21 is: One tablet orally once daily for 21 days, followed by 7 days off, then repeat.. 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 NORTREL 1/35-21 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. NORTREL 1/35-21 is classified as Category C. Category X. First trimester: No increased risk of major birth defects observed in clinical studies, but postmarketing data are insufficient. Second and third trimesters: Use associ. 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.