Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NORTREL 1/35-21 vs AFIRMELLE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Combination of ethinyl estradiol (estrogen) and norethindrone (progestin) suppresses gonadotropin (FSH and LH) release from the pituitary, inhibiting ovulation, altering cervical mucus to impede sperm penetration, and inducing endometrial changes that reduce implantation likelihood.
Combination oral contraceptive containing ethinyl estradiol and levonorgestrel. Inhibits ovulation by suppressing gonadotropin release (FSH and LH). Also increases cervical mucus viscosity and alters endometrial receptivity.
Prevention of pregnancy,Oral contraception
Prevention of pregnancy (FDA-approved)
One tablet orally once daily for 21 days, followed by 7 days off, then repeat.
One tablet (0.1 mg levonorgestrel, 0.02 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days of placebo.
Norethindrone: 5-14 hours; Ethinyl estradiol: 17-24 hours. Steady-state achieved after 10 days.
Terminal elimination half-life: 12–15 hours. Steady-state achieved within 5 days with Q12H dosing.
Ethinyl estradiol undergoes hepatic metabolism primarily via CYP3A4 hydroxylation and conjugation; norethindrone is metabolized primarily via reduction and sulfate/glucuronide conjugation.
Ethinyl estradiol undergoes first-pass metabolism in gut and liver via CYP3A4, with conjugation to sulfate and glucuronide. Levonorgestrel is metabolized primarily by CYP3A4 to reduced and hydroxylated metabolites, then conjugated.
Renal 50-60% as metabolites, fecal 40-50% as conjugates, <1% unchanged
Renal: 50% as unchanged drug and metabolites; fecal: 40% as metabolites; biliary: ~10% as glucuronide conjugates.
Norethindrone: 80% bound to albumin and SHBG; Ethinyl estradiol: 98% bound to albumin and SHBG.
~99% bound to serum albumin and sex hormone-binding globulin.
Norethindrone: 2-4 L/kg; Ethinyl estradiol: 3-5 L/kg. Indicates extensive tissue distribution.
2.8 L/kg (apparent Vd), indicating extensive tissue distribution.
Oral: Norethindrone ~65% (first-pass metabolism), Ethinyl estradiol ~40-50% (first-pass metabolism).
Oral: ~70% due to first-pass metabolism.
No dose adjustment required for renal impairment; use with caution in severe impairment.
No dose adjustment required for mild to moderate renal impairment. Not recommended for use in end-stage renal disease.
Contraindicated in acute liver disease, hepatocellular carcinoma, or active hepatitis. In Child-Pugh A: no adjustment; Child-Pugh B or C: contraindicated.
Contraindicated in acute hepatic disease or severe (Child-Pugh C) hepatic impairment. Use with caution in mild to moderate hepatic impairment; monitor liver function.
Not indicated for use before menarche; after menarche, same as adult dosing.
Not indicated for use before menarche. Post-menarche: same as adult dosing (one tablet daily) based on adult clinical trials.
No specific dose adjustment; estrogen-containing contraceptives are generally not recommended after menopause.
Not indicated for use in postmenopausal women; no specific dose adjustment required in healthy elderly, but limited data available.
Cigarette smoking increases risk of serious cardiovascular events from combination hormonal contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day) and is significant in women over 35. Women over 35 who smoke should not use this product.
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptive use. Risk increases with age (especially in women over 35) and with heavy smoking (15+ cigarettes/day). Women who use combination hormonal contraceptives should be strongly advised not to smoke.
Thrombotic disorders (venous thromboembolism, stroke, myocardial infarction) – discontinue if occur or suspected,Elevated risk of thromboembolic events in smokers, especially over 35,Increased risk of gallbladder disease,Hepatic neoplasia (benign and malignant) – discontinue if jaundice or liver function abnormalities develop,Elevated blood pressure – monitor regularly,Carbohydrate and lipid metabolism effects – monitor in diabetic or hyperlipidemic patients,Ocular lesions (retinal thrombosis) – discontinue if unexplained vision loss occurs,Headache – evaluate if new or worsening migraine patterns,Uterine bleeding irregularities – rule out pregnancy or pathology
Thrombotic disorders (venous thromboembolism, stroke, myocardial infarction),Cigarette smoking (increases cardiovascular risk),Hypertension (especially in women with renal disease or migraines),Gallbladder disease,Hepatic neoplasia (benign and malignant),Carbohydrate and lipid metabolism effects,Ocular lesions (retinal thrombosis),Depressed mood or depression,Uterine bleeding irregularities,Reduced efficacy with hepatic enzyme inducers
Thrombophlebitis or thromboembolic disorders (current or history),Cerebrovascular or coronary artery disease,Known or suspected breast carcinoma or estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Pregnancy (known or suspected),Hepatic adenoma or carcinoma (benign or malignant liver tumors),Jaundice or impaired liver function (active liver disease),Hypersensitivity to any component,Smoking in women over 35,Uncontrolled hypertension,Diabetes with vascular involvement,Migraine with focal neurological symptoms (if over 35)
Thrombophlebitis or thromboembolic disorders (current or history),Cerebrovascular or coronary artery disease (current or history),Known or suspected breast cancer, endometrial cancer, or other estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Cholestatic jaundice of pregnancy or jaundice with prior oral contraceptive use,Hepatic adenoma or carcinoma (current or history),Known or suspected pregnancy,Hypersensitivity to any component of the product,Heavy smoking (≥15 cigarettes/day) in women over 35
No specific food restrictions; however, grapefruit juice may increase estrogen levels; avoid excessive consumption. Maintain consistent dietary patterns to avoid gastrointestinal interference with absorption.
Grapefruit juice may increase ethinyl estradiol levels; avoid large quantities. No significant food restrictions. Administer with food if GI upset occurs.
Category X. First trimester: No increased risk of major birth defects observed in clinical studies, but postmarketing data are insufficient. Second and third trimesters: Use associated with fetal harm, including cardiovascular defects, limb defects, and masculinization of female fetuses. Avoid during pregnancy.
Pregnancy category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: exposure associated with congenital anomalies (e.g., cardiovascular, neural tube defects). Second and third trimesters: increased risk of fetal growth restriction, preterm birth, and neonatal respiratory distress. Postnatal: possible long-term developmental effects.
Excreted in breast milk in small amounts; M/P ratio for estrogen is 0.2, for progestin is 0.3. No adverse effects reported in nursing infants. American Academy of Pediatrics considers use compatible with breastfeeding, but may reduce milk production and quality. Use only if clearly needed.
Contraindicated during breastfeeding. Small amounts of ethinyl estradiol and norethindrone are excreted in breast milk; M/P ratio not well defined. Potential for adverse effects on infant (e.g., jaundice, breast enlargement). May reduce milk production and quality.
No dose adjustment required; drug is contraindicated in pregnancy. If inadvertently used, discontinue immediately.
Contraindicated in pregnancy; no dose adjustment recommended. If exposure occurs, immediate discontinuation is required. No pharmacokinetic data support safe use; avoid use entirely.
Nortrel 1/35-21 is a monophasic combined oral contraceptive containing 1 mg norethindrone and 35 mcg ethinyl estradiol. Administer 21 active tablets followed by 7 placebo tablets. Advise patients to take at the same time daily. Missed doses increase pregnancy risk; use backup contraception if missed. Not recommended in patients with BMI > 35 due to increased failure risk. Contraindicated in smokers over 35 years old.
Afirmelle (levonorgestrel/ethinyl estradiol) is a combined oral contraceptive. Counsel patients to take at the same time daily to maintain consistent hormone levels. Use back-up contraception if a dose is missed. Monitor for signs of thromboembolism, especially in smokers over 35. Advise that certain antibiotics (e.g., rifampin) and anticonvulsants (e.g., phenytoin) may reduce efficacy. Consider progestin-only pill if contraindications to estrogen exist.
Take one pill at the same time each day, starting on the first day of your menstrual period.,If you miss a dose, take it as soon as remembered, and use a backup method for 7 days.,Do not smoke while taking this medication, especially if over 35 years old.,Common side effects include nausea, breast tenderness, and breakthrough bleeding.,Inform your doctor if you have liver disease, blood clots, breast cancer, or high blood pressure.
Take one pill at the same time every day, even if you don't have sex.,If you miss a pill, follow the instructions in the package insert or ask your healthcare provider.,Use a backup method (like condoms) if you start late or miss pills.,This medication does not protect against HIV or other sexually transmitted infections.,Common side effects include nausea, breast tenderness, and breakthrough bleeding.,Seek medical help if you have symptoms of a blood clot: sudden chest pain, leg swelling, or shortness of breath.,Smoking while on this pill increases your risk of serious cardiovascular events.
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 NORTREL 1/35-21 vs AFIRMELLE, answered by our medical review team.
NORTREL 1/35-21 is a Oral Contraceptive that works by Combination of ethinyl estradiol (estrogen) and norethindrone (progestin) suppresses gonadotropin (FSH and LH) release from the pituitary, inhibiting ovulation, altering cervical mucus to impede sperm penetration, and inducing endometrial changes that reduce implantation likelihood.. AFIRMELLE is a Combined Oral Contraceptive that works by Combination oral contraceptive containing ethinyl estradiol and levonorgestrel. Inhibits ovulation by suppressing gonadotropin release (FSH and LH). Also increases cervical mucus viscosity and alters endometrial receptivity.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NORTREL 1/35-21 and AFIRMELLE 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 NORTREL 1/35-21 is: One tablet orally once daily for 21 days, followed by 7 days off, then repeat.. The standard adult dose of AFIRMELLE is: One tablet (0.1 mg levonorgestrel, 0.02 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days of placebo.. 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 NORTREL 1/35-21 and AFIRMELLE 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. NORTREL 1/35-21 is classified as Category C. Category X. First trimester: No increased risk of major birth defects observed in clinical studies, but postmarketing data are insufficient. Second and third trimesters: Use associ. AFIRMELLE is classified as Category C. Pregnancy category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: exposure associated with congenital anomalies (e.g., cardiovascular, neural tube defe. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.