Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
GILDESS FE 1/20 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 oral contraceptive: ethinyl estradiol suppresses gonadotropin release; norethindrone induces progestational changes in endometrium and cervical mucus, preventing ovulation and fertilization.
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,Treatment of moderate acne vulgaris (for females ≥15 years old who have menarche and desire contraception),Oral contraceptive for women with iron deficiency anemia (as Gildess Fe 1/20 contains ferrous fumarate)
Prevention of pregnancy (FDA-approved)
One tablet orally once daily for 21 days followed by 7 placebo tablets per 28-day cycle.
One tablet (0.1 mg levonorgestrel, 0.02 mg ethinyl estradiol) orally once daily for 21 days, followed by 7 days of placebo.
Ethinyl estradiol: terminal half-life approximately 13 hours (range 10-15 h). Desogestrel: metabolized to etonogestrel; etonogestrel terminal half-life about 28 hours (range 20-40 h). Clinical context: steady-state reached within 7-10 days.
Terminal elimination half-life: 12–15 hours. Steady-state achieved within 5 days with Q12H dosing.
Ethinyl estradiol undergoes CYP3A4-mediated hydroxylation; norethindrone is reduced and conjugated via glucuronidation and sulfation.
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.
Approximately 60-65% renal (as metabolites), 30-35% fecal (as metabolites and unchanged drug). Ethinyl estradiol and desogestrel metabolites are excreted primarily via urine and feces. Etonogestrel (active metabolite) is excreted mainly via feces (40%) and urine (32%).
Renal: 50% as unchanged drug and metabolites; fecal: 40% as metabolites; biliary: ~10% as glucuronide conjugates.
Ethinyl estradiol: 97-98% bound to albumin, with specific binding to sex hormone-binding globulin (SHBG). Etonogestrel: >95% bound, primarily to albumin (60-70%) and SHBG (30-40%).
~99% bound to serum albumin and sex hormone-binding globulin.
Ethinyl estradiol: apparent Vd approximately 2.5 L/kg (range 2.1-3.0 L/kg). Desogestrel: Vd for etonogestrel is about 2.0 L/kg. High Vd indicates extensive tissue distribution, including adipose and reproductive tissues.
2.8 L/kg (apparent Vd), indicating extensive tissue distribution.
Oral: Ethinyl estradiol bioavailability approximately 45-55% due to first-pass metabolism (sulfation and glucuronidation). Desogestrel: prodrug, bioavailability of etonogestrel is about 76-84% after oral dose. No other relevant routes.
Oral: ~70% due to first-pass metabolism.
No dose adjustment required for mild to moderate renal impairment. Contraindicated in severe renal impairment (Cr Cl <30 m L/min) due to potential for fluid retention.
No dose adjustment required for mild to moderate renal impairment. Not recommended for use in end-stage renal disease.
Contraindicated in severe hepatic impairment (Child-Pugh class C). Caution in moderate impairment (Child-Pugh class B) due to altered hormone metabolism; use alternative methods if possible.
Contraindicated in acute hepatic disease or severe (Child-Pugh C) hepatic impairment. Use with caution in mild to moderate hepatic impairment; monitor liver function.
Approved for postmenarchal adolescents; dosing same as adults: one tablet orally once daily for 21 days followed by 7 placebo tablets.
Not indicated for use before menarche. Post-menarche: same as adult dosing (one tablet daily) based on adult clinical trials.
Not typically indicated for postmenopausal women due to ineffectiveness; if used in appropriate patients, no dose adjustment required but monitor for thromboembolic risks.
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 oral contraceptives. Risk increases with age and smoking intensity (≥15 cigarettes/day) and is significant in women >35 years old. Women >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 (thrombophlebitis, venous thromboembolism, stroke, MI),Carcinoma of the breast and reproductive organs,Hepatic disease (adenoma, hepatocellular carcinoma),Ocular lesions (retinal thrombosis),Gallbladder disease,Carbohydrate and lipid effects,Elevated blood pressure,Headache/migraine,Bleeding irregularities,Depression,Hereditary angioedema,Chloasma,Hepatic function impairment,Iron supplementation (Fe fumarate): may cause GI upset, constipation, and dark stools
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,Cerebrovascular or coronary artery disease,Known or suspected breast carcinoma,Endometrial or other estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Pregnancy or suspected pregnancy,Benign or malignant liver tumor,Active liver disease,Hypersensitivity to any component,Smoking in women >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 significant food interactions. However, grapefruit juice may inhibit CYP3A4 metabolism and theoretically increase estrogen levels, but clinical significance is undetermined. Avoid St. John's wort, which reduces contraceptive efficacy. Caffeine metabolism may be decreased, leading to increased caffeine effects. No specific dietary restrictions required.
Grapefruit juice may increase ethinyl estradiol levels; avoid large quantities. No significant food restrictions. Administer with food if GI upset occurs.
FDA Pregnancy Category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: Increased risk of neural tube defects, congenital heart defects, and limb reduction defects from progestin component. Second and third trimesters: Risk of fetal feminization (masculinization of female fetuses) from androgen-like effects of progestin; also associated with increased risk of neonatal hepatoblastoma and possibly other tumors. Combination hormonal contraceptives should be discontinued immediately if pregnancy occurs.
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 (estrogen and progestin). M/P ratio not well-defined. Use may reduce milk production and quality, especially in early postpartum period. Consider alternative contraception during breastfeeding, especially in first 6 months. Use only if benefits outweigh risks, with close monitoring of infant growth and development.
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 indicated as use is not recommended. If inadvertently taken during pregnancy, discontinue immediately. No dosage changes are suggested for postpartum use, but alternative contraception should be considered during breastfeeding.
Contraindicated in pregnancy; no dose adjustment recommended. If exposure occurs, immediate discontinuation is required. No pharmacokinetic data support safe use; avoid use entirely.
Gildess FE 1/20 is a monophasic oral contraceptive containing 20 mcg ethinyl estradiol and 1 mg norethindrone acetate with ferrous fumarate placebos. It is indicated for contraception and may be used off-label for acne. The low estrogen dose may lead to more breakthrough bleeding, especially in the first few cycles. Advise patients to take at the same time daily and not to skip active pills. The iron in placebos can cause dark stools; warn patients. Missed pill management: if one active pill is missed, take it as soon as remembered; if two are missed, take two and use backup contraception for 7 days. Consider CYP3A4 inducers (e.g., rifampin, certain anticonvulsants) which reduce efficacy. Not recommended in patients with BMI > 35 due to increased failure risk. Do not use in smokers over 35 years old. Monitor blood pressure and for thrombotic events.
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, even during withdrawal bleed weeks.,If you miss a pill, follow the package instructions: take the missed pill immediately and continue; if more than one missed, use backup contraception for 7 days.,The last 7 pills in the pack are placebo; they contain iron, so do not skip them but they don't provide contraceptive protection.,Iron in placebos may cause dark stools; this is harmless.,Common side effects: nausea, breast tenderness, headache, breakthrough bleeding (especially first 3 months). These often improve with time.,Contact your doctor if you have severe abdominal pain, chest pain, shortness of breath, severe headaches, vision changes, or leg pain/swelling.,This pill does not protect against sexually transmitted infections (STIs). Use condoms for STI prevention.,Avoid smoking while taking this medication, especially if over 35 years old.,Tell your doctor about all medications, especially antibiotics, antifungals, and seizure medications, as they may decrease effectiveness.,If you are undergoing surgery, inform your surgeon you are taking this pill.
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 GILDESS FE 1/20 vs AFIRMELLE, answered by our medical review team.
GILDESS FE 1/20 is a Oral Contraceptive that works by Combination oral contraceptive: ethinyl estradiol suppresses gonadotropin release; norethindrone induces progestational changes in endometrium and cervical mucus, preventing ovulation and fertilization.. 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 GILDESS FE 1/20 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 GILDESS FE 1/20 is: One tablet orally once daily for 21 days followed by 7 placebo tablets per 28-day cycle.. 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 GILDESS FE 1/20 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. GILDESS FE 1/20 is classified as Category C. FDA Pregnancy Category X. Contraindicated in pregnancy due to risk of fetal harm. First trimester: Increased risk of neural tube defects, congenital heart defects, and limb reducti. 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.