Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PHILITH vs ALYACEN 1/35
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
PHILITH is a combined oral contraceptive containing ethinyl estradiol and drospirenone. Ethinyl estradiol suppresses gonadotropin release, while drospirenone is a progestin with antiandrogenic and antimineralocorticoid activity, inhibiting ovulation and altering cervical mucus.
Combination hormonal contraceptive: ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; norethindrone induces progestational effects including cervical mucus thickening and endometrial changes, inhibiting ovulation and sperm penetration.
Prevention of pregnancy,Treatment of moderate acne vulgaris in women at least 14 years old who have no known contraindications to oral contraceptive therapy and have achieved menarche,Treatment of premenstrual dysphoric disorder (PMDD) in women of reproductive age
Prevention of pregnancy
1 mg orally once daily
One tablet (norethindrone 1 mg and ethinyl estradiol 35 mcg) orally once daily for 21 consecutive days, followed by 7 days of placebo or no tablets.
Terminal half-life 12 hours; clinically relevant for twice-daily dosing with steady state reached after 2-3 days.
Norethindrone: 8-11 hours (terminal); ethinyl estradiol: 10-20 hours (terminal). The half-life supports once-daily dosing for oral contraceptive efficacy.
Ethinyl estradiol is metabolized primarily by CYP3A4, with sulfation and glucuronidation; drospirenone is metabolized by CYP3A4.
Ethinyl estradiol: primarily hepatic via CYP3A4; norethindrone: hepatic reduction and sulfate conjugation.
Renal: 90% unchanged; biliary/fecal: 10% as metabolites.
Renal excretion of metabolites (primarily ethinyl estradiol and norethindrone conjugates) accounts for approximately 50-60% of elimination; fecal excretion accounts for 30-40%. Unchanged drug excretion is minimal (<5%).
98% bound to albumin.
Norethindrone: 61% bound to albumin and SHBG; ethinyl estradiol: 97-98% bound to albumin.
0.3 L/kg; suggests limited extravascular distribution.
Norethindrone: 3.8-4.5 L/kg; ethinyl estradiol: 2.0-4.0 L/kg. Large Vd indicates extensive tissue distribution.
Oral: 80% (high first-pass metabolism).
Oral: Norethindrone ~64%, ethinyl estradiol ~38-48% (due to first-pass metabolism).
GFR 30-89 m L/min: no adjustment; GFR 15-29 m L/min: 0.5 mg once daily; GFR <15 m L/min: not recommended
No dose adjustment required for mild to moderate renal impairment. Contraindicated in severe renal impairment or acute renal failure due to potential fluid retention and electrolyte disturbances.
Child-Pugh A: no adjustment; Child-Pugh B: 0.5 mg once daily; Child-Pugh C: not recommended
Contraindicated in patients with hepatic impairment, including Child-Pugh class B or C, due to impaired metabolism of estrogen and progestin. Not recommended in patients with active liver disease or history of liver tumors.
Not approved for use in children under 18 years
Not indicated for use before menarche. For postmenarchal adolescents, same dosing as adults. Safety and efficacy established for contraception; weight-based dosing not applicable.
No specific adjustment; monitor renal function and adjust per renal guidelines
Not indicated for use after menopause due to lack of benefit and increased risks (e.g., cardiovascular, thromboembolic events). If used, monitor for fluid retention, hypertension, and glucose intolerance.
Cigarette smoking increases the risk of serious cardiovascular events from combination oral contraceptive use. This risk increases with age and with heavy smoking (15 or more cigarettes per day) and is quite marked in women over 35 years of age. Women who use combination oral contraceptives should be strongly advised not to smoke.
Cigarette smoking increases risk of serious cardiovascular events from combined oral contraceptives. Risk increases with age and heavy smoking (≥15 cigarettes/day). Women over 35 who smoke should not use this product.
Increased risk of thromboembolic and thrombotic disorders (e.g., venous thromboembolism, stroke, myocardial infarction) especially in smokers over 35,Elevated blood pressure,Gallbladder disease,Carbohydrate and lipid metabolic effects,Hepatic neoplasia risk,Increased risk of pancreatitis due to hypertriglyceridemia,Chloasma (melasma) possibly persistent,Hereditary angioedema exacerbation in women with C1 esterase inhibitor deficiency,Impaired liver function
Thrombotic disorders (e.g., DVT, PE, stroke, MI),Cerebrovascular disease,Hepatic neoplasia,Gallbladder disease,Hypertension,Carbohydrate and lipid effects,Ocular lesions,Hereditary angioedema,Chloasma,Menstrual irregularities,Pregnancy exclusion prior to initiation
Pregnancy,Current or history of thrombophlebitis or venous thromboembolic disorders,Cerebrovascular or coronary artery disease,Known or suspected breast carcinoma or other estrogen-dependent neoplasia,Undiagnosed abnormal genital bleeding,Hepatic adenoma or carcinoma,Jaundice or cholestatic jaundice of pregnancy or prior pill use,Known hypersensitivity to any component,Smoking over age 35,Uncontrolled hypertension,Diabetes with vascular involvement,Migraine with focal aura,Severe renal insufficiency or adrenal insufficiency (due to drospirenone's antimineralocorticoid effect)
Venous or arterial thrombotic/thromboembolic disease (current or history),Cerebrovascular disease,Coronary artery disease,Known or suspected breast cancer,Endometrial 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 in women over 35
Grapefruit and grapefruit juice may increase estrogen levels, leading to increased side effects. St. John's Wort may decrease contraceptive effectiveness. Avoid excessive alcohol consumption as it may increase liver enzyme induction and reduce efficacy.
No significant food interactions. Grapefruit juice may increase estrogen levels, but clinically not a concern. Avoid excessive alcohol, which may impair liver function and increase estrogen exposure. Maintain a healthy diet, as weight gain is possible.
PHILITH is contraindicated in pregnancy. First trimester exposure carries high risk of neural tube defects, cardiac anomalies, and cleft palate based on animal studies and limited human data. Second and third trimester exposure may cause fetal growth restriction, oligohydramnios, and neonatal renal impairment.
Pregnancy category X. Use of ALYACEN 1/35 (norethindrone/ethinyl estradiol) is contraindicated during pregnancy. First trimester: Increased risk of congenital anomalies, including cardiovascular defects and limb reduction defects. Second/third trimesters: Potential for urogenital abnormalities and feminization of male fetus. Exposure is associated with subsequent development of clear cell adenocarcinoma of vagina/cervix in female offspring (DES-related).
It is unknown whether PHILITH is excreted in human milk. Due to potential for serious adverse reactions in nursing infants, breastfeeding is not recommended during therapy and for 2 weeks after last dose. M/P ratio is not available.
Small amounts of contraceptive steroids and/or metabolites have been identified in breast milk. M/P ratio: Not specifically determined for this combination; ethinyl estradiol M/P ratio ~0.02-0.04. Use may reduce milk production and quality. Breastfeeding not recommended during use. Alternative contraception advised.
PHILITH is contraindicated in pregnancy; no dose adjustment can be recommended. Physiologic increases in renal clearance and hepatic metabolism during pregnancy may reduce drug exposure, but the teratogenic risk precludes use. If inadvertent exposure occurs, immediately discontinue and consider alternative therapy.
Contraindicated in pregnancy; no dose adjustments applicable. Discontinue medication immediately upon pregnancy detection.
PHILITH is a combination oral contraceptive containing ethinyl estradiol and progestin. Monitor for thromboembolic events; avoid in smokers over 35. Start on first day of menses or first Sunday after onset. Missed dose management: if missed >48 hours, use backup contraception for 7 days.
ALYACEN 1/35 is a combination oral contraceptive containing ethinyl estradiol 35 mcg and norgestimate 1 mg. It is indicated for the prevention of pregnancy and for the treatment of moderate acne vulgaris in females ≥15 years of age who desire an oral contraceptive. Monitor for thromboembolic events, especially in smokers over 35 or those with migraine with aura. Use with caution in patients with liver impairment or history of cholestatic jaundice. The pill-free interval should not exceed 7 days; missed pills increase ovulation risk. Consider non-hormonal backup if vomiting or diarrhea occurs within 4 hours of dosing.
Take one pill daily at same time; missed pills increase pregnancy risk.,Do not smoke while taking this medication; smoking increases risk of blood clots.,Use backup contraception (e.g., condoms) if you miss two or more pills.,Contact healthcare provider if you experience leg pain, chest pain, shortness of breath, or severe headache.,The medication does not protect against sexually transmitted infections.,You may have spotting or nausea initially; these usually improve.
Take one tablet daily at the same time each day; do not skip doses.,Use an additional non-hormonal contraceptive (e.g., condoms) if you miss a pill, have vomiting, or diarrhea.,Smoking while on this pill increases the risk of blood clots and stroke, especially if you are over 35.,Contact your healthcare provider immediately if you have chest pain, leg pain/swelling, sudden vision changes, or severe headache.,This medication does not protect against HIV or other sexually transmitted infections.,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 PHILITH vs ALYACEN 1/35, answered by our medical review team.
PHILITH is a Oral Contraceptive that works by PHILITH is a combined oral contraceptive containing ethinyl estradiol and drospirenone. Ethinyl estradiol suppresses gonadotropin release, while drospirenone is a progestin with antiandrogenic and antimineralocorticoid activity, inhibiting ovulation and altering cervical mucus.. ALYACEN 1/35 is a Oral Contraceptive that works by Combination hormonal contraceptive: ethinyl estradiol suppresses gonadotropin release via negative feedback on hypothalamic-pituitary axis; norethindrone induces progestational effects including cervical mucus thickening and endometrial changes, inhibiting ovulation and sperm penetration.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PHILITH and ALYACEN 1/35 depend on the specific clinical indication. These are both Oral Contraceptive agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of PHILITH is: 1 mg orally once daily. The standard adult dose of ALYACEN 1/35 is: One tablet (norethindrone 1 mg and ethinyl estradiol 35 mcg) orally once daily for 21 consecutive days, followed by 7 days of placebo or no tablets.. 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 PHILITH and ALYACEN 1/35 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. PHILITH is classified as Category C. PHILITH is contraindicated in pregnancy. First trimester exposure carries high risk of neural tube defects, cardiac anomalies, and cleft palate based on animal studies and limited . ALYACEN 1/35 is classified as Category C. Pregnancy category X. Use of ALYACEN 1/35 (norethindrone/ethinyl estradiol) is contraindicated during pregnancy. First trimester: Increased risk of congenital anomalies, including . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.