Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
LEVORA 0.15/30-21 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 oral contraceptive: ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; levonorgestrel inhibits ovulation and thickens cervical mucus, impairing sperm penetration. Also induces endometrial atrophy.
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 21 days, followed by 7 tablet-free days.
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.
20-30 hours for ethinyl estradiol; 2-4 hours for levonorgestrel. Steady-state reached in 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.
Levonorgestrel: hepatically metabolized via CYP3A4, CYP2C19, and CYP2C9; undergoes conjugation. Ethinyl estradiol: metabolized via CYP3A4 and sulfation (SULT1E1).
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Urine (50-60% as metabolites), feces (30-40% as glucuronides); <10% 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%).
Levonorgestrel: 97-98% (SHBG, albumin); Ethinyl estradiol: 97-98% (albumin, SHBG)
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
Levonorgestrel: 1.4 L/kg; Ethinyl estradiol: 2.4 L/kg; 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: levonorgestrel ~100%; ethinyl estradiol 38-48% (first-pass metabolism)
Oral: Norethindrone ~64%, ethinyl estradiol ~38-48% (due to first-pass metabolism).
No dose adjustment required for mild to moderate renal impairment. Not studied in severe renal impairment; use caution.
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 or severe (Child-Pugh C) hepatic impairment. For Child-Pugh A or B, use is not recommended; alternative contraception advised.
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. For postmenarchal adolescents, same dosing as adults: one tablet orally once daily for 21 days, then 7 days off.
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 geriatric dosing considerations due to lack of indication.
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. Risk increases with age and smoking intensity (especially >35 years). Women >35 years who smoke should not use combination oral contraceptives.
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 (DVT, PE, stroke, MI),Cerebral hemorrhage,Hepatic neoplasia (benign/malignant),Gallbladder disease,Hypertension,Carbohydrate/lipid metabolism effects,Ocular lesions (e.g., retinal thrombosis),Headache/migraine,Uterine bleeding irregularities,Depression,Contact lens intolerance
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
Hypersensitivity to any component,Thrombophlebitis or thromboembolic disorders (current or history),Cerebrovascular or coronary artery disease (current or history),Known or suspected breast carcinoma,Estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Cholestatic jaundice of pregnancy or jaundice with prior oral contraceptive use,Hepatic adenoma or carcinoma,Pregnancy (known or suspected),Heavy smoking (>15 cigarettes/day) in women ≥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 specific food restrictions. Grapefruit juice may increase estrogen levels; avoid large quantities. Maintain consistent dietary habits to avoid 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.
First trimester: No increased risk of birth defects based on large epidemiological studies. Second and third trimesters: Avoid use due to potential adverse effects on fetal development, including feminization of male fetuses and hepatic adenoma. Overall, pregnancy is a contraindication for levonorgestrel/ethinyl estradiol.
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).
Levonorgestrel and ethinyl estradiol are excreted in breast milk. M/P ratio for levonorgestrel is approximately 1.0; for ethinyl estradiol, it is 0.4. Use may reduce milk production and composition. Not recommended during lactation.
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 are applicable as use is contraindicated during pregnancy. Pharmacokinetic changes in pregnancy (increased volume of distribution, altered hepatic metabolism) would require dose modification if use were considered, but no established guidelines exist.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
Levonorgestrel/ethinyl estradiol is a combination oral contraceptive. Advise patients to take at the same time daily. Breakthrough bleeding is more common in first few cycles. Missed pill management: if less than 12 hours, take immediately; if more than 12 hours, check package insert. Consider drug interactions with rifampin, certain anticonvulsants, and antibiotics. Not recommended in smokers over 35 and those with history of migraines with aura, hypertension, or thromboembolism.
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 every day.,If you miss a pill, refer to the patient leaflet for instructions.,Use backup contraception (e.g., condoms) if you miss pills or have vomiting/diarrhea.,Common side effects include nausea, spotting, and breast tenderness; these often improve after 3 months.,Do not smoke while taking this medication, especially if over age 35.,This medication does not protect against HIV or other sexually transmitted infections.
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 LEVORA 0.15/30-21 vs ALYACEN 1/35, answered by our medical review team.
LEVORA 0.15/30-21 is a Oral Contraceptive that works by Combination oral contraceptive: ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; levonorgestrel inhibits ovulation and thickens cervical mucus, impairing sperm penetration. Also induces endometrial atrophy.. 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 LEVORA 0.15/30-21 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 LEVORA 0.15/30-21 is: One tablet orally once daily for 21 days, followed by 7 tablet-free days.. 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 LEVORA 0.15/30-21 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. LEVORA 0.15/30-21 is classified as Category C. First trimester: No increased risk of birth defects based on large epidemiological studies. Second and third trimesters: Avoid use due to potential adverse effects on fetal develop. 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.