Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PORTIA-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 oral contraceptive: estrogen (ethinyl estradiol) suppresses gonadotropin release, inhibiting ovulation; progestin (levonorgestrel) alters 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 (levonorgestrel 0.15 mg, ethinyl estradiol 0.03 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.
Levonorgestrel: 24-30 hours; ethinyl estradiol: 12-15 hours. Clinical context: Steady-state achieved 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.
Hepatic: ethinyl estradiol and levonorgestrel are metabolized via CYP3A4, conjugation, and sulfation.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Renal (60-70% as metabolites, 20-30% as levonorgestrel/ethinyl estradiol glucuronides), fecal (10-20%), biliary (minor).
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: 97.5-99% to sex hormone-binding globulin (SHBG) and albumin; ethinyl estradiol: 98-99% to albumin.
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
Levonorgestrel: 1.8 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 ~40-45% (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
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 hepatic disease or severe cirrhosis (Child-Pugh C); use with caution in mild to moderate hepatic impairment
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.
Use only after menarche; dose as per adult schedule (one tablet daily)
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 postmenopausal women
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 oral contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day). 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.
Increased risk of thromboembolic disorders (VTE, MI, stroke),Hepatic neoplasia,Hypertension,Gallbladder disease,Carbohydrate/lipid metabolism effects,Bleeding irregularities
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,Cerebrovascular or coronary artery disease,Known or suspected pregnancy,Undiagnosed abnormal genital bleeding,Known or suspected breast cancer,Liver tumors or active liver disease,Hypersensitivity to any component,Use with Hepatitis C drug combinations containing ombitasvir/paritaprevir/ritonavir with or without dasabuvir
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
Grapefruit and grapefruit juice may increase ethinyl estradiol levels and risk of adverse effects; avoid concurrent consumption. No other significant food interactions. Maintain consistent dietary habits as changes in diet may affect drug absorption. Do not consume alcohol excessively as it may increase risk of liver toxicity and reduce contraceptive efficacy.
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. First trimester exposure associated with cardiovascular defects, neural tube defects, and limb reduction anomalies. Second and third trimester exposure may cause fetal adrenal suppression, virilization of female fetuses due to progestin component, and potential long-term neurodevelopmental effects. Postnatal effects include possible behavioral issues.
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 into breast milk. M/P ratio not well established; progestins and estrogens are present in low levels. Potential for adverse effects on infant such as jaundice and breast enlargement. Generally not recommended during breastfeeding; alternative contraception advised.
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; contraindicated in pregnancy. No dose adjustment recommendations exist as use is contraindicated.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
Portia-28 is a combination oral contraceptive (COC) containing ethinyl estradiol and levonorgestrel. Initiate on the first day of menstrual bleeding or the first Sunday after onset; if starting after day 5, use backup contraception for 7 days. Missed pill management: if one pill is missed, take it as soon as remembered and continue regular schedule (may take two pills in one day); if two or more pills are missed, take the most recent missed pill, discard others, use backup contraception for 7 days, and consider emergency contraception if unprotected intercourse occurred. Maximum efficacy requires daily adherence at the same time. CYP3A4 inducers (e.g., rifampin, St. John's wort) may reduce contraceptive effectiveness; consider alternative non-hormonal methods during co-administration. Portia-28 may increase serum potassium; caution with potassium-sparing diuretics, ACE inhibitors, or ARBs. Discontinue if migraines with aura, unexplained visual loss, or signs of thromboembolism occur. Monitor blood pressure and liver function periodically.
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, with or without food. Do not skip doses.,If you miss a pill, refer to the missed pill instructions in the package insert; use backup contraception if needed.,Portia-28 does not protect against HIV or other sexually transmitted infections; use condoms for STI prevention.,Smoking increases risk of serious cardiovascular events; avoid smoking, especially if over age 35.,Contact your healthcare provider immediately if you experience chest pain, shortness of breath, leg swelling, severe headache, vision changes, or jaundice.,Inform your doctor of all medications you take, including over-the-counter drugs and herbal supplements.,Store at room temperature away from moisture and heat; keep out of reach of children.
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 PORTIA-28 vs ALYACEN 1/35, answered by our medical review team.
PORTIA-28 is a Oral Contraceptive that works by Combination oral contraceptive: estrogen (ethinyl estradiol) suppresses gonadotropin release, inhibiting ovulation; progestin (levonorgestrel) alters 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 PORTIA-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 PORTIA-28 is: One tablet (levonorgestrel 0.15 mg, ethinyl estradiol 0.03 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 PORTIA-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. PORTIA-28 is classified as Category C. Pregnancy category X. Contraindicated in pregnancy. First trimester exposure associated with cardiovascular defects, neural tube defects, and limb reduction anomalies. Second and t. 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.