Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NORTREL 1/35-28 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 and norethindrone inhibits gonadotropin secretion via negative feedback on the hypothalamic-pituitary-ovarian axis, suppressing ovulation. Additionally, increases cervical mucus viscosity and alters endometrial receptivity.
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
Prevention of pregnancy (FDA-approved)
One tablet (norethindrone 1 mg + ethinyl estradiol 35 mcg) orally once daily for 28 days, followed by a 7-day placebo period (if using 28-day pack) or continuous if using 21-day pack with 7-day off. Start on first day of menstrual period.
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 (terminal); ethinyl estradiol: 13-27 hours (terminal). Context: steady-state after 5-7 days; dose adjustment in hepatic impairment.
Terminal elimination half-life: 12–15 hours. Steady-state achieved within 5 days with Q12H dosing.
Primarily hepatic via CYP3A4; ethinyl estradiol undergoes first-pass metabolism; norethindrone is metabolized via reduction and 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 60-70% (as glucuronide and sulfate conjugates), fecal 20-30% (via biliary excretion).
Renal: 50% as unchanged drug and metabolites; fecal: 40% as metabolites; biliary: ~10% as glucuronide conjugates.
Norethindrone: 99% bound (SHBG, albumin); ethinyl estradiol: 98% bound (albumin, SHBG).
~99% bound to serum albumin and sex hormone-binding globulin.
Norethindrone: 4-5 L/kg (extensive tissue distribution); ethinyl estradiol: 2-4 L/kg (significant tissue uptake).
2.8 L/kg (apparent Vd), indicating extensive tissue distribution.
Norethindrone: 47-73% (oral); ethinyl estradiol: 38-48% (oral, first-pass metabolism).
Oral: ~70% due to first-pass metabolism.
No dose adjustment required for mild to moderate renal impairment (GFR >=30 m L/min). Not recommended for use in severe renal impairment (GFR <30 m L/min) due to potential for hormonal disturbances and adverse effects.
No dose adjustment required for mild to moderate renal impairment. Not recommended for use in end-stage renal disease.
Contraindicated in acute liver disease, active hepatitis, or severe cirrhosis (Child-Pugh class C). For mild (Child-Pugh A) or moderate (Child-Pugh B) impairment, use is not recommended due to potential for altered metabolism; alternative contraception advised.
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 in postmenarchal pediatric patients; safety and efficacy established for contraception in females of reproductive age. For adolescents, standard adult dosing may be used after menarche; individualize based on clinical judgment.
Not indicated for use before menarche. Post-menarche: same as adult dosing (one tablet daily) based on adult clinical trials.
Not indicated for use in postmenopausal women; estrogen-containing contraceptives are not appropriate for this age group. No specific geriatric dosage adjustments applicable as therapy is not recommended.
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 side effects from 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 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.
Increased risk of thromboembolic disorders,Cigarette smoking increases cardiovascular risk,Elevated blood pressure,Hepatic neoplasia,Gallbladder disease,Glucose intolerance,Ocular lesions (e.g., retinal thrombosis),Headache/migraine,Menstrual irregularities and breakthrough bleeding
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,History of deep vein thrombosis or pulmonary embolism,Cerebrovascular or coronary artery disease,Known or suspected breast cancer,Carcinoma of the endometrium 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 and age >35 years (relative contraindication)
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
Grapefruit and grapefruit juice may increase ethinyl estradiol levels and risk of adverse effects. Avoid grapefruit products. No other significant food interactions; however, maintain consistent dietary habits as high-fat meals may delay absorption but not reduce overall bioavailability.
Grapefruit juice may increase ethinyl estradiol levels; avoid large quantities. No significant food restrictions. Administer with food if GI upset occurs.
Pregnancy category X. Significant risk of fetal harm in the first trimester (limb defects, cardiac anomalies) and second/third trimesters (genital abnormalities, neurodevelopmental effects). Use contraindicated in 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. M/P ratio approximately 0.4. May reduce milk production and affect infant hormonal balance. Use with caution, monitor infant for jaundice and growth.
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 dosing adjustments required as drug is contraindicated in pregnancy. No pharmacokinetic data available for dose modification.
Contraindicated in pregnancy; no dose adjustment recommended. If exposure occurs, immediate discontinuation is required. No pharmacokinetic data support safe use; avoid use entirely.
NORTREL 1/35-28 contains norethindrone 1 mg and ethinyl estradiol 35 mcg. For COCs, consider that CYP3A4 inducers (e.g., rifampin, St. John's wort) may reduce contraceptive efficacy. If a patient misses two or more pills, use backup contraception for 7 days. The 28-day pack includes 21 active pills and 7 placebo pills to maintain the regimen.
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 daily at the same time for 28 days; start the next pack immediately after finishing the current pack.,Do not skip pills; if you miss one, take it as soon as remembered. If you miss two or more, use backup contraception for 7 days.,This drug does not protect against HIV or other sexually transmitted infections.,Common side effects include nausea, headache, breast tenderness, and spotting. Contact your provider if you have severe abdominal pain, chest pain, or leg pain.,Do not smoke; smoking increases the risk of serious cardiovascular side effects, especially in women over 35.
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 1/35-28 vs AFIRMELLE, answered by our medical review team.
NORTREL 1/35-28 is a Oral Contraceptive that works by Combination of ethinyl estradiol and norethindrone inhibits gonadotropin secretion via negative feedback on the hypothalamic-pituitary-ovarian axis, suppressing ovulation. Additionally, increases cervical mucus viscosity and alters endometrial receptivity.. 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 1/35-28 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 1/35-28 is: One tablet (norethindrone 1 mg + ethinyl estradiol 35 mcg) orally once daily for 28 days, followed by a 7-day placebo period (if using 28-day pack) or continuous if using 21-day pack with 7-day off. Start on first day of menstrual period.. 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 1/35-28 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 1/35-28 is classified as Category C. Pregnancy category X. Significant risk of fetal harm in the first trimester (limb defects, cardiac anomalies) and second/third trimesters (genital abnormalities, neurodevelopmental. 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.