Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NORLESTRIN FE 2.5/50 vs ALTAVERA
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 norethindrone (progestin) and ethinyl estradiol (estrogen). Inhibits ovulation by suppressing gonadotropin-releasing hormone (Gn RH) via negative feedback on the hypothalamus and pituitary. Increases cervical mucus viscosity to impede sperm penetration and induces endometrial atrophy to prevent implantation.
Combination of ethinyl estradiol and desogestrel: ethinyl estradiol suppresses gonadotropin release, inhibiting ovulation; desogestrel (progestin) causes cervical mucus thickening and endometrial atrophy, preventing implantation.
Prevention of pregnancy (FDA-approved),Treatment of moderate acne vulgaris (in women ≥15 years who desire oral contraception, have no contraindications, and have not achieved success with topical agents),Management of menstrual disorders (off-label)
Prevention of pregnancy,Treatment of moderate acne vulgaris (in females ≥15 years with no contraindications)
One tablet orally once daily, each containing 2.5 mg norethindrone acetate and 50 mcg ethinyl estradiol, plus 7 iron tablets (75 mg ferrous fumarate) taken during the placebo week.
1 tablet (ethinyl estradiol 0.03 mg / levonorgestrel 0.15 mg) orally once daily for 21 days, followed by 7 placebo days.
Norethindrone: ~8-10 hours (terminal), requiring daily dosing for stable contraceptive effect. Ethinyl estradiol: ~13-21 hours (terminal), supporting once-daily administration.
Levonorgestrel: terminal elimination half-life 25±10 hours; ethinyl estradiol: 13±7 hours. Clinical context: steady-state concentrations achieved within 5-7 days; contraceptive efficacy requires consistent daily dosing.
Hepatic metabolism via cytochrome P450 (CYP) enzymes: ethinyl estradiol is primarily metabolized by CYP3A4; norethindrone undergoes reduction, hydroxylation, and conjugation. Both undergo enterohepatic recirculation and are excreted in urine and feces.
Ethinyl estradiol: primarily metabolized by CYP3A4; undergoes sulfation and glucuronidation. Desogestrel: rapidly converted to active metabolite etonogestrel via CYP2C9 and CYP2C19; further metabolism by CYP3A4.
Norethindrone: ~80% renal (as glucuronide and sulfate conjugates), ~20% fecal. Ethinyl estradiol: ~40% renal, ~60% fecal, with enterohepatic recirculation.
Renal excretion of metabolites and unchanged drug: ~30% (levonorgestrel) and ~20% (ethinyl estradiol) in urine; biliary/fecal elimination: ~40-50% as conjugates and metabolites.
Norethindrone: ~61-70% bound to albumin and SHBG. Ethinyl estradiol: ~97-98% bound to albumin.
Levonorgestrel: 98-99% bound to sex hormone-binding globulin (SHBG) and albumin; ethinyl estradiol: 98% bound to albumin.
Norethindrone: Vd ~1.8-4.5 L/kg (extensive tissue distribution). Ethinyl estradiol: Vd ~2.5-5 L/kg (distributes into breast milk).
Levonorgestrel: Vd ~1.8 L/kg (suggesting extensive tissue distribution). Ethinyl estradiol: Vd ~2.4 L/kg.
Norethindrone: ~64% (oral). Ethinyl estradiol: ~38-48% (oral) due to first-pass metabolism.
Oral bioavailability: levonorgestrel ~100% (nearly complete); ethinyl estradiol ~45-50% (first-pass hepatic metabolism).
No specific dose adjustment provided; contraindicated in severe renal impairment (GFR <30 m L/min) due to potential fluid retention.
No dose adjustment required for mild to moderate renal impairment. Contraindicated in severe renal disease or acute renal failure due to potential fluid retention.
Contraindicated in severe hepatic disease (Child-Pugh class C); use with caution in mild to moderate impairment (Child-Pugh A or B) with monitoring for adverse effects; no specific dose reduction guidelines established.
Contraindicated in severe hepatic dysfunction (Child-Pugh class B or C). Use caution in mild to moderate impairment (Child-Pugh A); monitor liver enzymes.
Not indicated for use before menarche; post-menarche: same as adult dosing (one tablet daily) after menstrual cycle establishment.
Not indicated for use before menarche. For postmenarchal adolescents, same dosing as adults (1 tablet daily, 21/7 regimen) after evaluation of risks.
Not indicated for postmenopausal women; no dose adjustment in elderly with normal hepatic and renal function, but consider increased risk of thromboembolic events and metabolic effects.
Not indicated for postmenopausal women. No specific geriatric dosing; consider increased risk of thromboembolism, cardiovascular disease, and metabolic effects in older women of reproductive age.
Cigarette smoking increases the risk of serious cardiovascular events (e.g., myocardial infarction, stroke, thromboembolism) from combination oral contraceptive use. Risk increases with age and number of cigarettes smoked. Women over 35 years who smoke should not use this combination oral contraceptive.
Cigarette smoking increases risk of serious cardiovascular events from combined oral contraceptives. Risk increases with age (especially >35 years) and with number of cigarettes smoked. Women who use combined hormonal contraceptives should be strongly advised not to smoke.
Thromboembolic disorders: increased risk of venous thromboembolism (VTE) and arterial thrombosis; discontinue if suspected,Cardiovascular disease: increased risk of myocardial infarction and stroke, especially in smokers >35 years,Hypertension: may develop or worsen; monitor blood pressure,Cervical cancer: controversial association; Pap smear screening recommended,Hepatic neoplasia: rare but reported; contraindicated with active liver disease,Gallbladder disease: increased risk of cholelithiasis,Ocular effects: retinal thrombosis may occur; discontinue if sudden partial or complete vision loss,Carbohydrate metabolism: may decrease glucose tolerance; monitor diabetic patients,Fluid retention: use with caution in conditions affected by edema (e.g., migraine, asthma, renal impairment)
Thrombotic disorders: risk of venous thromboembolism (VTE), stroke, myocardial infarction; discontinue if thrombotic event occurs.,Hepatic disease: discontinue if jaundice or liver function abnormalities develop.,Hypertension: monitor blood pressure; discontinue if uncontrolled.,Carbohydrate metabolism: may affect glucose tolerance; monitor diabetic patients.,Depression: discontinue if significant depression occurs.,Gallbladder disease: increased risk of cholelithiasis.
Thrombophlebitis or thromboembolic disorders (current or history),Cerebrovascular or coronary artery disease (current or history),Known or suspected breast carcinoma, endometrial carcinoma, or estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Pregnancy (known or suspected),Benign or malignant liver tumor (current or history),Active liver disease (e.g., acute viral hepatitis) or impaired liver function,Hypersensitivity to any component of the product,Cigarette smoking in women over 35 years of age
Thrombophlebitis or thromboembolic disorders (current or history),Cerebrovascular or coronary artery disease (current or history),Known or suspected breast carcinoma,Estrogen-dependent neoplasia (known or suspected),Undiagnosed abnormal genital bleeding,Cholestatic jaundice of pregnancy or jaundice with prior pill use,Hepatic adenoma or carcinoma (known or suspected),Pregnancy (known or suspected),Hypersensitivity to any component
Avoid grapefruit and grapefruit juice as they may increase estrogen levels and side effects. No specific food restrictions otherwise. Iron from ferrous fumarate may be affected by calcium-rich foods or supplements; take iron at least 2 hours apart from dairy products.
No significant food interactions. Alcohol does not affect efficacy but may increase risk of adverse effects such as nausea. Grapefruit juice has no known interaction. Avoid excessive alcohol consumption due to potential hepatotoxicity.
NORLESTRIN FE 2.5/50 (norethindrone acetate 2.5 mg/ethinyl estradiol 0.05 mg) is contraindicated in pregnancy. First trimester: increased risk of congenital anomalies including cardiovascular and limb defects, and possible non-genital malformations. Second/third trimester: feminization of male fetus, vaginal adenosis, and cervical changes in females. Exposure is associated with a 1.3 to 2.0-fold increased risk of congenital heart defects.
ALTAVERA contains ethinyl estradiol and levonorgestrel. First trimester: Inadvertent exposure during organogenesis is associated with a very low absolute risk of cardiovascular defects (relative risk 1.2-1.4) and no consistent increase in other major malformations. Second and third trimesters: No known teratogenic effects, but theoretical risks from estrogenic effects (e.g., feminization of male fetus). Postnatal: No increased risk of long-term developmental effects from pregnancy exposure.
Norethindrone and ethinyl estradiol are excreted into breast milk. M/P ratio for norethindrone is approximately 1.1; for ethinyl estradiol approximately 0.3. Use during lactation may reduce milk production and quality. Not recommended for nursing mothers.
Combined oral contraceptives may reduce milk production and quality, especially in early lactation. Ethinyl estradiol transfers into breast milk at low levels (M/P ratio approximately 0.1-0.2), excluding clinical effects in term infants. Levonorgestrel transfer is minimal (M/P ratio ~0.2-0.4). Use is generally avoided in breastfeeding women, especially during the first 6 weeks postpartum. Progestin-only methods are preferred.
No dosing adjustments are applicable as drug is contraindicated in pregnancy. Higher baseline estradiol levels in pregnancy do not necessitate dose changes because use is not recommended.
Contraindicated in pregnancy. No dose adjustment recommended because use is discontinued upon confirmed or suspected pregnancy. Pharmacokinetic changes in pregnancy (e.g., increased hepatic clearance, altered binding proteins) are not relevant for this indication.
NORLESTRIN FE 2.5/50 contains norethindrone 2.5 mg and ethinyl estradiol 50 mcg, plus ferrous fumarate (75 mg) as a placebo. The high estrogen dose (50 mcg) increases thromboembolic risk; avoid in patients with migraine with aura, hypertension, or smoking >35 years. Iron supplementation can cause dark stools. The formulation includes 7 iron-containing placebo tablets to maintain cycle control and prevent iron deficiency.
ALTAVERA is a combined oral contraceptive (COC) containing ethinylestradiol and levonorgestrel. It inhibits ovulation via suppression of gonadotropins. Counsel patients to take at the same time daily to maintain efficacy. Missed pill management: if missed within 12 hours, take immediately; if >12 hours, take last missed pill and use backup contraception for 7 days. Be aware of increased VTE risk, especially in smokers over 35. May reduce effectiveness of lamotrigine; monitor seizure control. Initiate on the first day of menses or first Sunday after onset.
Take one tablet daily at the same time, preferably after an evening meal to reduce nausea.,Missed dose: If one day, take as soon as remembered; if two days, take two tablets then resume schedule; if more, use backup contraception and consult healthcare provider.,Report signs of blood clots: chest pain, sudden shortness of breath, leg pain/swelling, or severe headache.,Iron supplements may cause dark stools; this is harmless.,Do not smoke while taking this medication as it increases risk of serious cardiovascular side effects.,Antibiotics (e.g., rifampin), anticonvulsants, and St. John's Wort may decrease effectiveness; use alternative contraception.
Take one tablet daily at the same time each day, with or without food.,If you miss a pill by less than 12 hours, take it as soon as you remember. If more than 12 hours, take the missed pill and use a backup method (e.g., condoms) for the next 7 days.,Smoking increases your risk of serious cardiovascular side effects, especially if you are over 35 years old. Do not smoke while taking this medication.,Seek immediate medical attention if you experience sudden severe headache, chest pain, leg pain/swelling, or vision changes (symptoms of blood clots).,This medication does not protect against HIV or other sexually transmitted infections.,If you are taking lamotrigine or other anticonvulsants, tell your doctor; your seizure medication may be less effective.,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 NORLESTRIN FE 2.5/50 vs ALTAVERA, answered by our medical review team.
NORLESTRIN FE 2.5/50 is a Oral Contraceptive that works by Combination oral contraceptive containing norethindrone (progestin) and ethinyl estradiol (estrogen). Inhibits ovulation by suppressing gonadotropin-releasing hormone (Gn RH) via negative feedback on the hypothalamus and pituitary. Increases cervical mucus viscosity to impede sperm penetration and induces endometrial atrophy to prevent implantation.. ALTAVERA is a Combined Oral Contraceptive that works by Combination of ethinyl estradiol and desogestrel: ethinyl estradiol suppresses gonadotropin release, inhibiting ovulation; desogestrel (progestin) causes cervical mucus thickening and endometrial atrophy, preventing implantation.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NORLESTRIN FE 2.5/50 and ALTAVERA 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 NORLESTRIN FE 2.5/50 is: One tablet orally once daily, each containing 2.5 mg norethindrone acetate and 50 mcg ethinyl estradiol, plus 7 iron tablets (75 mg ferrous fumarate) taken during the placebo week.. The standard adult dose of ALTAVERA is: 1 tablet (ethinyl estradiol 0.03 mg / levonorgestrel 0.15 mg) orally once daily for 21 days, followed by 7 placebo days.. 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 NORLESTRIN FE 2.5/50 and ALTAVERA 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. NORLESTRIN FE 2.5/50 is classified as Category C. NORLESTRIN FE 2.5/50 (norethindrone acetate 2.5 mg/ethinyl estradiol 0.05 mg) is contraindicated in pregnancy. First trimester: increased risk of congenital anomalies including car. ALTAVERA is classified as Category C. ALTAVERA contains ethinyl estradiol and levonorgestrel. First trimester: Inadvertent exposure during organogenesis is associated with a very low absolute risk of cardiovascular def. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.