Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NORTREL 0.5/35-28 vs AFIRMELLE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Norethindrone and ethinyl estradiol are a combination hormonal contraceptive. Norethindrone suppresses gonadotropin release (FSH and LH) from the pituitary, inhibiting ovulation. Ethinyl estradiol stabilizes the endometrium and enhances the contraceptive effect by inhibiting gonadotropin secretion.
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 contraceptive (off-label: treatment of acne, abnormal uterine bleeding, dysmenorrhea)
Prevention of pregnancy (FDA-approved)
1 tablet orally once daily for 28 days (21 active tablets containing 0.5 mg norethindrone and 35 mcg ethinyl estradiol, followed by 7 placebo tablets).
One tablet (0.1 mg levonorgestrel, 0.02 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days of placebo.
Norethindrone: 7.2-9.2 hours; Ethinyl estradiol: 13-27 hours. Clinical context: Steady state reached in 5-7 days; half-life supports once-daily dosing.
Terminal elimination half-life: 12–15 hours. Steady-state achieved within 5 days with Q12H dosing.
Norethindrone: primarily hepatic via reduction and sulfation; CYP3A4 involved. Ethinyl estradiol: hepatic via CYP3A4; undergoes first-pass metabolism and enterohepatic recirculation.
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: ~40% as metabolites; Biliary/Fecal: ~60% as metabolites; <5% unchanged.
Renal: 50% as unchanged drug and metabolites; fecal: 40% as metabolites; biliary: ~10% as glucuronide conjugates.
Norethindrone: 61% bound to albumin, 36% to SHBG; Ethinyl estradiol: 97% bound to albumin, 2% free.
~99% bound to serum albumin and sex hormone-binding globulin.
Norethindrone: 3.6-4.3 L/kg; Ethinyl estradiol: 2.3-3.7 L/kg; indicates extensive tissue distribution.
2.8 L/kg (apparent Vd), indicating extensive tissue distribution.
Oral: Norethindrone ~64% (extensive first-pass metabolism); Ethinyl estradiol ~43-45% (due to first-pass and gut wall metabolism).
Oral: ~70% due to first-pass metabolism.
No dose adjustment required for GFR ≥30 m L/min. Use is not recommended in patients with GFR <30 m L/min or on dialysis due to potential decrease in hormone clearance and increased risk of adverse effects.
No dose adjustment required for mild to moderate renal impairment. Not recommended for use in end-stage renal disease.
Contraindicated in patients with Child-Pugh class B or C hepatic impairment. For Child-Pugh class A, use is not recommended due to potential reduced hormone metabolism.
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 pediatric patients before menarche. For post-menarcheal adolescents, dosing is same as adults: 1 tablet orally once daily for 28 days.
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. No specific dosing adjustments for elderly patients as the drug is not used in this population for contraception.
Not indicated for use in postmenopausal women; no specific dose adjustment required in healthy elderly, but limited data available.
Cigarette smoking increases the risk of serious cardiovascular events from combined hormonal contraceptive use. The risk increases with age and heavy smoking (≥15 cigarettes per day) and is significant in women over 35 years old. Women over 35 who smoke should not use combined hormonal contraceptives.
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 thrombotic disorders (venous thromboembolism, stroke, myocardial infarction),Hepatic neoplasia (benign and malignant),Elevated blood pressure,Gallbladder disease,Carbohydrate/lipid metabolism effects,Headache/migraine,Irregular bleeding,Ocular changes (retinal thrombosis),Depression,Hereditary angioedema,Pregnancy (discontinue if pregnancy occurs)
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
Known or suspected pregnancy,Current or history of venous thrombotic disease (deep vein thrombosis, pulmonary embolism),Cerebrovascular or coronary artery disease,Current or history of migraine with aura (if age ≥35),Breast cancer or other estrogen-sensitive neoplasia,Undiagnosed abnormal genital bleeding,Cholestatic jaundice of pregnancy or jaundice with prior oral contraceptive use,Active liver disease or benign/malignant liver tumors,Hypersensitivity to any component,Smoking cigarettes and age >35 years
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. Grapefruit juice may increase ethinyl estradiol levels; avoid large amounts. Alcohol may increase risk of liver toxicity; limit intake.
Grapefruit juice may increase ethinyl estradiol levels; avoid large quantities. No significant food restrictions. Administer with food if GI upset occurs.
First trimester: No increased risk of major birth defects based on large cohort studies. Second and third trimesters: Associated with masculinization of female fetuses (clitoral hypertrophy, labial fusion) and possible altered pubertal development. Risk of pseudohermaphroditism is dose-dependent.
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.
Norethindrone and ethinyl estradiol are excreted in breast milk. Estrogen components may reduce milk production. M/P ratio for norethindrone is approximately 0.7; ethinyl estradiol is <1. Use is generally not recommended during lactation.
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.
Contraindicated in pregnancy; no dose adjustments recommended. Discontinue immediately if pregnancy occurs.
Contraindicated in pregnancy; no dose adjustment recommended. If exposure occurs, immediate discontinuation is required. No pharmacokinetic data support safe use; avoid use entirely.
NORTREL 0.5/35-28 is a monophasic combined oral contraceptive containing 0.5 mg norethindrone and 35 mcg ethinyl estradiol. Administer daily at the same time. Breakthrough bleeding is common in the first 3-6 months. Monitor blood pressure at baseline and annually. Consider VTE risk in smokers over 35. Missed pill protocol: if one pill is missed, take as soon as remembered; if two or more, use backup contraception for 7 days.
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, in the order shown on the blister pack.,If you miss a pill, follow the package insert instructions and use backup contraception if needed.,Common side effects include nausea, breast tenderness, and spotting between periods.,Do not smoke while taking this medication, especially if over 35 years old.,Report symptoms of blood clots, including leg pain/swelling, chest pain, or sudden shortness of breath.,This medication does not protect against HIV or other sexually transmitted infections.
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 0.5/35-28 vs AFIRMELLE, answered by our medical review team.
NORTREL 0.5/35-28 is a Oral Contraceptive that works by Norethindrone and ethinyl estradiol are a combination hormonal contraceptive. Norethindrone suppresses gonadotropin release (FSH and LH) from the pituitary, inhibiting ovulation. Ethinyl estradiol stabilizes the endometrium and enhances the contraceptive effect by inhibiting gonadotropin secretion.. 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 0.5/35-28 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 0.5/35-28 is: 1 tablet orally once daily for 28 days (21 active tablets containing 0.5 mg norethindrone and 35 mcg ethinyl estradiol, followed by 7 placebo tablets).. 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 0.5/35-28 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 0.5/35-28 is classified as Category C. First trimester: No increased risk of major birth defects based on large cohort studies. Second and third trimesters: Associated with masculinization of female fetuses (clitoral hy. 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.