Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
OVULEN-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 estrogen-progestin oral contraceptive that inhibits ovulation primarily by suppressing gonadotropin-releasing hormone (Gn RH) from the hypothalamus, reducing follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion, and altering cervical mucus and endometrial lining.
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 (ethinyl estradiol 0.05 mg / ethynodiol diacetate 1 mg) orally once daily for 21 days followed by 7 days placebo; continuous cycle.
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: 13-27 hours (mean ~17 hours); Norethindrone: 5-14 hours (mean ~8 hours). Clinical context: Steady state reached 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 is primarily metabolized via CYP3A4; ethynodiol diacetate undergoes extensive first-pass metabolism, converted to norethindrone and other metabolites.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Renal: ~50% as metabolites; Fecal/biliary: ~40% as conjugated metabolites; <1% unchanged in urine.
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: 98-99% bound (albumin, SHBG); Norethindrone: 80-85% bound (albumin, SHBG).
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
Ethinyl estradiol: 2.3-3.2 L/kg (extensive tissue distribution); Norethindrone: 2.1-2.8 L/kg (distribution consistent with steroid hormones).
Norethindrone: 3.8-4.5 L/kg; ethinyl estradiol: 2.0-4.0 L/kg. Large Vd indicates extensive tissue distribution.
Ethinyl estradiol: 38-48% (extensive first-pass metabolism); Norethindrone: 50-77% (oral bioavailability).
Oral: Norethindrone ~64%, ethinyl estradiol ~38-48% (due to first-pass metabolism).
No dose adjustment required for mild to moderate renal impairment; use with caution in severe 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 acute or chronic liver disease, including hepatic adenomas or carcinoma; discontinue if jaundice develops.
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; postmenarche: same as adult dosing after assessment of bone age and growth potential.
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 use after menopause; no specific dose adjustment, but consider increased risk of thromboembolic events and estrogen-dependent neoplasms.
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 the risk of serious cardiovascular events (e.g., myocardial infarction, thromboembolism, stroke) from combination oral contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day), particularly in women over 35.
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 thrombotic disorders (e.g., venous thromboembolism, arterial thromboembolism), cardiovascular events, hepatic neoplasia, and gallbladder disease. Discontinue if jaundice or visual disturbances occur. Monitor for hypertension, depression, and fluid retention.
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; history of deep-vein thrombosis or pulmonary embolism; cerebrovascular or coronary artery disease; known or suspected breast carcinoma; estrogen-dependent neoplasia; undiagnosed abnormal genital bleeding; known or suspected pregnancy; hepatic adenoma or carcinoma; active liver disease; hypersensitivity to any component.
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. May be taken with or without food. Grapefruit juice may increase estrogen levels; avoid excessive consumption.
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 exposure is associated with increased risk of noncardiac birth defects (e.g., limb reduction defects) and cardiac anomalies (e.g., VSD, TGA). Postnatal studies show no increased risk with second or third trimester use. Avoid use in pregnancy due to known risks.
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 low amounts; M/P ratio ~0.3. No adverse effects reported in breastfed infants. Use with caution only if necessary.
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 pharmacokinetic data inform dose adjustments; contraindicated in pregnancy.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
Ovulen-28 (ethynodiol diacetate 1 mg/mestranol 0.1 mg) is a first-generation combined oral contraceptive. Counsel patients to take at the same time daily. If a dose is missed, follow standard missed pill protocol. Drug interactions with rifampin, anticonvulsants, and certain antibiotics may reduce efficacy. Monitor for hypertension, thromboembolism, and liver dysfunction. Not recommended for smokers over 35. Assess for contraindications including history of DVT, stroke, or migraine with aura.
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 daily at the same time, even during your period.,If you miss a pill, take it as soon as you remember; if more than 12 hours late, use backup contraception.,Ovulen-28 does not protect against HIV or other STDs.,Common side effects include nausea, breast tenderness, and spotting; these usually improve.,Report symptoms of blood clots (leg pain, chest pain, sudden headache or vision changes) immediately.,Avoid smoking, especially if over 35, due to increased risk of serious side effects.,Tell your doctor about all other medications you take.,Store at room temperature away from moisture and heat.
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 OVULEN-28 vs ALYACEN 1/35, answered by our medical review team.
OVULEN-28 is a Oral Contraceptive that works by Combination estrogen-progestin oral contraceptive that inhibits ovulation primarily by suppressing gonadotropin-releasing hormone (Gn RH) from the hypothalamus, reducing follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion, and altering cervical mucus and endometrial lining.. 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 OVULEN-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 OVULEN-28 is: One tablet (ethinyl estradiol 0.05 mg / ethynodiol diacetate 1 mg) orally once daily for 21 days followed by 7 days placebo; continuous cycle.. 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 OVULEN-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. OVULEN-28 is classified as Category C. First trimester exposure is associated with increased risk of noncardiac birth defects (e.g., limb reduction defects) and cardiac anomalies (e.g., VSD, TGA). Postnatal studies show. 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.