Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
FOUNDAYO 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
Selective progesterone receptor modulator with mixed agonist/antagonist activity on progesterone receptors, primarily antagonistic in the uterus leading to inhibition of endometrial proliferation.
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.
FDA-approved: Treatment of heavy menstrual bleeding due to uterine fibroids.,Off-label: Emergency contraception.
Prevention of pregnancy
100 mg orally once daily
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.
Terminal elimination half-life is 3-4 hours in healthy adults; prolonged to 6-8 hours in moderate renal impairment (Cr Cl 30-50 m L/min) and up to 12 hours in severe renal impairment (Cr Cl <30 m L/min).
Norethindrone: 8-11 hours (terminal); ethinyl estradiol: 10-20 hours (terminal). The half-life supports once-daily dosing for oral contraceptive efficacy.
Primarily metabolized by CYP3A4 to active metabolites; undergoes further metabolism by CYP1A2 and CYP2C19.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Primarily renal (80-90% as unchanged drug), with 10-20% fecal via biliary excretion. Less than 5% metabolized.
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%).
85-90% bound to albumin. Minor binding to alpha-1-acid glycoprotein.
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
0.8-1.2 L/kg, indicating distribution into total body water and some tissue binding. Increased in neonates and elderly.
Norethindrone: 3.8-4.5 L/kg; ethinyl estradiol: 2.0-4.0 L/kg. Large Vd indicates extensive tissue distribution.
Oral: 70-80% due to moderate first-pass metabolism. Subcutaneous: 90-100%. Intramuscular: 85-95%.
Oral: Norethindrone ~64%, ethinyl estradiol ~38-48% (due to first-pass metabolism).
e GFR ≥30 m L/min: No adjustment. e GFR <30 m L/min: Not recommended.
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.
Child-Pugh A: No adjustment. Child-Pugh B: Use with caution, reduce dose to 50 mg once daily. Child-Pugh C: Not recommended.
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.
Safety and efficacy not established in pediatric patients.
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 recommended; monitor renal function.
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.
No FDA black box warning.
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.
Risk of ectopic pregnancy: Rule out before treatment.,Pregnancy category X: Contraindicated in pregnancy due to fetal harm.,Endometrial changes: Chronic use may cause endometrial hyperplasia or thickening.,Liver enzymes: Monitor ALT/AST; discontinue if significant elevation.,Cushingoid effects: Prolonged use may lead to adrenal insufficiency.
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
Known or suspected pregnancy.,Hypersensitivity to ulipristal acetate or any component.,Concurrent use of progestin-containing contraceptives.
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 known food interactions. Maintain usual diet.
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: Increased risk of major congenital malformations, including neural tube defects and cardiovascular anomalies. Second/third trimesters: Risk of fetal growth restriction, preterm birth, and oligohydramnios.
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).
Excretion into human milk unknown. M/P ratio not available. Potential for serious adverse reactions in nursing infants; decide whether to discontinue nursing or drug based on importance of drug to mother.
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 recommended; however, pharmacokinetic changes in pregnancy may reduce exposure. Therapeutic drug monitoring advised to maintain efficacy and avoid toxicity.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
FOUNDAYO is a monoclonal antibody targeting IL-23. Pre-treatment screening for latent tuberculosis is mandatory. Administer subcutaneously; rotate injection sites. Monitor for hypersensitivity reactions during infusion. Avoid live vaccines during treatment.
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.
Store in refrigerator, do not freeze. Protect from light.,Inject as prescribed; rotate sites (abdomen, thigh, upper arm).,Report signs of infection (fever, cough, skin redness) immediately.,Avoid live vaccines (e.g., MMR, varicella) during therapy.,Seek medical help for allergic reactions (hives, difficulty breathing).
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 FOUNDAYO vs ALYACEN 1/35, answered by our medical review team.
FOUNDAYO is a Oral contraceptive that works by Selective progesterone receptor modulator with mixed agonist/antagonist activity on progesterone receptors, primarily antagonistic in the uterus leading to inhibition of endometrial proliferation.. 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 FOUNDAYO and ALYACEN 1/35 depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of FOUNDAYO is: 100 mg orally once daily. 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 FOUNDAYO 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. FOUNDAYO is classified as Category C. First trimester: Increased risk of major congenital malformations, including neural tube defects and cardiovascular anomalies. Second/third trimesters: Risk of fetal growth restric. 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.