Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CYCLAFEM 1/35 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 containing ethinyl estradiol and norethindrone. Suppresses gonadotropin (FSH, LH) secretion via estrogen and progestin negative feedback, inhibiting ovulation. Progestin alters cervical mucus (sperm penetration) and endometrial receptivity.
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. Each tablet contains 1 mg norethindrone and 0.035 mg ethinyl estradiol. Administer daily for 21 days followed by 7 days of placebo or no tablet.
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.
Half-life of norethindrone is 5-14 hours; ethinyl estradiol is 10-20 hours. Steady state reached after 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: CYP3A4, sulfation, glucuronidation. Norethindrone: CYP3A4, reduction, conjugation.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Renal 40-60% as glucuronide and sulfate conjugates, biliary/fecal 20-40%.
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 is 80-85% bound to SHBG and albumin; ethinyl estradiol is 95-98% bound to albumin.
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
Norethindrone Vd is 1.2-2.4 L/kg; ethinyl estradiol Vd is 2.5-4.5 L/kg.
Norethindrone: 3.8-4.5 L/kg; ethinyl estradiol: 2.0-4.0 L/kg. Large Vd indicates extensive tissue distribution.
Oral bioavailability: norethindrone 50-60%; ethinyl estradiol 40-50% due to 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. Contraindicated in severe renal disease or acute renal failure 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 Child-Pugh class B or C (moderate to severe hepatic impairment). For Child-Pugh class A, use with caution and monitor liver function; no specific dose adjustment studied.
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 in postmenarchal minors before menarche. For adolescents, same adult dosing (one tablet daily) after menarche. Safety and efficacy established in postmenarchal females.
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 in postmenopausal women. Avoid use in women over 50 years due to increased risk of thrombosis and no benefit for contraception. If used, no specific dose adjustment, but consider non-hormonal alternatives.
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 COC use. Risk increases with age and heavy smoking (>=15 cigarettes/day). Women over 35 who smoke should not use COCs.
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, MI, stroke),Hepatic neoplasia (benign and malignant),Elevated blood pressure,Gallbladder disease,Carbohydrate/lipid metabolic effects,Hereditary angioedema exacerbation,Chloasma,Ocular lesions (retinal thrombosis, optic neuritis),Depression,Menstrual irregularities/breakthrough bleeding
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 DVT/PE,Cerebrovascular or coronary artery disease,Known or suspected breast carcinoma,Estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Cholestatic jaundice of pregnancy/COC-related jaundice,Benign/malignant hepatic adenoma,Pregnancy,Hypersensitivity to any component,Age >35 and smoking >=15 cigarettes/day
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. However, grapefruit juice may increase ethinyl estradiol levels via CYP3A4 inhibition, though clinical significance is uncertain. Avoid excessive alcohol intake as it may impair liver function and reduce contraceptive efficacy. Maintain a balanced diet, as folate supplementation may be beneficial due to potential folate depletion with oral contraceptives.
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.
Pregnancy category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: Increased risk of neural tube defects, cardiovascular anomalies, and limb reduction defects. Second and third trimesters: Associated with fetal genital abnormalities (masculinization of female fetuses) and potential for other congenital anomalies. Postnatal: Possible long-term neurodevelopmental effects.
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).
Compatible with breastfeeding. Norethindrone and ethinyl estradiol are excreted in breast milk in small amounts. M/P ratio: Norethindrone ~0.5-0.7; ethinyl estradiol ~0.1-0.3. No adverse effects reported in infants at recommended doses. May reduce milk volume and protein content; use lowest effective dose.
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.
Not applicable; drug is contraindicated during pregnancy. No dose adjustments are recommended because use is contraindicated. If inadvertent exposure occurs, discontinue immediately.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
CYCLAFEM 1/35 is a monophasic oral contraceptive containing norethindrone (1 mg) and ethinyl estradiol (35 mcg). For missed pills: if one pill is missed, take it as soon as remembered, even if it means taking two pills in one day. If two pills are missed in Week 1 or 2, take two pills on the day remembered and two the next day, then resume regular schedule; use backup contraception for 7 days. If two pills are missed in Week 3 or three or more pills are missed at any time, discard the rest of the pack and start a new pack that day; use backup contraception for 7 days. Monitor for breakthrough bleeding, which is common in the first few cycles. Avoid use in women with uncontrolled hypertension, migraine with aura, or history of 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 tablet daily at the same time each day; do not skip doses.,If you miss a pill, refer to the missed pill instructions in the package insert or consult your healthcare provider.,Use additional non-hormonal contraception (e.g., condoms) for 7 days after missing pills as directed.,Report any signs of thromboembolism (leg pain, chest pain, shortness of breath) or stroke (sudden severe headache, visual changes, speech difficulty) immediately.,Smoking increases the risk of serious cardiovascular side effects; avoid smoking while taking this medication.,This medication does not protect against HIV or other sexually transmitted infections.,Expect spotting or light bleeding between periods, especially in the first few months.,If you have vomiting or diarrhea, use backup contraception and consult your healthcare provider.
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 CYCLAFEM 1/35 vs ALYACEN 1/35, answered by our medical review team.
CYCLAFEM 1/35 is a Oral Contraceptive that works by Combination oral contraceptive containing ethinyl estradiol and norethindrone. Suppresses gonadotropin (FSH, LH) secretion via estrogen and progestin negative feedback, inhibiting ovulation. Progestin alters cervical mucus (sperm penetration) and endometrial receptivity.. 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 CYCLAFEM 1/35 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 CYCLAFEM 1/35 is: One tablet orally once daily. Each tablet contains 1 mg norethindrone and 0.035 mg ethinyl estradiol. Administer daily for 21 days followed by 7 days of placebo or no tablet.. 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 CYCLAFEM 1/35 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. CYCLAFEM 1/35 is classified as Category C. Pregnancy category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: Increased risk of neural tube defects, cardiovascular anomalies, and limb reduction d. 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.