ETHINYL ESTRADIOL AND LEVONORGESTREL
Clinical safety rating: avoid
Inducers of CYP450 enzymes (eg carbamazepine) may decrease estrogen levels Increases risk of thromboembolic disorders and endometrial cancer.
Combination hormonal contraceptive; ethinyl estradiol provides estrogenic activity, levonorgestrel provides progestational activity, suppressing gonadotropin (LH and FSH) release from the pituitary, inhibiting ovulation, and altering cervical mucus and endometrial lining to reduce sperm penetration and implantation.
| Metabolism | Ethinyl estradiol is metabolized primarily via CYP3A4; undergoes first-pass metabolism in the liver and gut wall; also undergoes glucuronidation and sulfation. Levonorgestrel is metabolized via reduction and conjugation; undergoes extensive hepatic metabolism, primarily via CYP3A4, and glucuronidation. |
| Excretion | Urine (40% ethinyl estradiol metabolites, 40% levonorgestrel metabolites); feces (40% ethinyl estradiol, 20% levonorgestrel). |
| Half-life | Ethinyl estradiol: 13-27 hours (terminal). Levonorgestrel: 18-30 hours (terminal). Clinical context: steady state achieved in 5-7 days; missed doses may require backup contraception. |
| Protein binding | Ethinyl estradiol: 97-98% bound (albumin and SHBG). Levonorgestrel: 97-99% bound (SHBG and albumin). |
| Volume of Distribution | Ethinyl estradiol: 2.5-5 L/kg. Levonorgestrel: 1.8-2.6 L/kg. Clinical meaning: extensive distribution into tissues, including breast and reproductive organs. |
| Bioavailability | Oral: Ethinyl estradiol 38-48% (first-pass metabolism). Levonorgestrel 100% (no first-pass effect). |
| Onset of Action | Oral: Inhibition of ovulation occurs within 2-3 days of first dose; contraceptive effect immediate if started on day 1 of menses. |
| Duration of Action | 24 hours for contraceptive efficacy. Clinical note: missed pill >24 hours reduces contraceptive reliability; backup needed if >48 hours. |
| Molecular Weight | Ethinyl estradiol: 296.4 Da; Levonorgestrel: 312.4 Da |
One tablet containing 0.02-0.05 mg ethinyl estradiol and 0.1-0.15 mg levonorgestrel orally once daily for 21 days, followed by 7 days of placebo or no tablets.
| Dosage form | TABLET |
| Renal impairment | No dosage adjustment required for mild to moderate renal impairment. Avoid use in severe renal failure (CrCl <30 mL/min) due to limited data and potential for decreased contraceptive efficacy. |
| Liver impairment | Contraindicated in Child-Pugh class B or C (moderate to severe hepatic impairment). Use with caution in Child-Pugh class A; monitor liver function. |
| Pediatric use | Same dosing as adults for postmenarchal adolescents. Use according to standard weight recommendations (≥42 kg for some formulations); consult specific product labeling. |
| Geriatric use | Not indicated for postmenopausal women due to lack of contraceptive need and increased risk of thromboembolic events and hormonal adverse effects. |
| 1st trimester | Contraindicated. Use during first trimester carries risk of congenital anomalies including cardiovascular and limb defects. Not recommended for use during pregnancy. |
| 2nd trimester | Contraindicated. Continued use associated with increased risk of adverse outcomes; no safe dose established. |
| 3rd trimester | Contraindicated. May cause fetal or neonatal harm due to hormonal effects; avoid in pregnant patients. |
Clinical note
Inducers of CYP450 enzymes (eg carbamazepine) may decrease estrogen levels Increases risk of thromboembolic disorders and endometrial cancer.
| FDA category | Positive |
| Placental transfer | Both components cross the placenta; ethinyl estradiol and levonorgestrel are transferred to fetal circulation, with potential for hormonal effects on developing fetus. |
■ FDA Black Box Warning
Cigarette smoking increases risk of serious cardiovascular events from combination oral contraceptive use. Risk increases with age and smoking ≥15 cigarettes per day. Women over 35 who smoke should not use this product.
| Common Effects | osteoporosis prevention |
| Serious Effects |
PregnancyThrombophlebitis or thromboembolic disordersHistory of deep vein thrombosis or pulmonary embolismCerebrovascular or coronary artery diseaseKnown or suspected breast carcinomaEndometrial carcinoma or other estrogen-dependent neoplasiaUndiagnosed abnormal genital bleedingCholestatic jaundice of pregnancy or jaundice with prior pill useHepatic adenoma or carcinomaKnown hypersensitivity to ethinyl estradiol or levonorgestrelAcute or chronic hepatocellular disease with abnormal liver functionSmoking in patients over 35 years of age (increases cardiovascular risk)
| Precautions | Increased risk of thromboembolic disorders (venous and arterial), Increased risk of myocardial infarction and stroke, especially in smokers over 35, Hepatic neoplasia (benign and malignant), Gallbladder disease, Elevated blood pressure, Carbohydrate and lipid metabolism effects, Headache including migraine, Unscheduled bleeding and spotting, Potential drug interactions (CYP3A4 inducers/inhibitors) |
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| Breastfeeding |
| Excreted in human milk. Both ethinyl estradiol and levonorgestrel are present in breast milk, and may reduce milk production and quality. Use only if clearly needed and benefits outweigh risks; monitor infant for adverse effects such as jaundice and breast enlargement. |
| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | Pregnancy category X. Contraindicated in pregnancy. First trimester: Increased risk of congenital anomalies, including cardiovascular defects and limb reduction defects, due to estrogenic and progestogenic effects. Second and third trimesters: No direct fetal risks as drug not used; if inadvertently continued, risk of maternal and fetal complications such as thromboembolism, jaundice, and fetal growth restriction. |
| Fetal Monitoring | Regular blood pressure monitoring, assessment for thromboembolic symptoms (leg pain, chest pain, dyspnea), liver function tests if jaundice, and pregnancy testing if withdrawal bleed missed. In case of unintentional use during pregnancy, ultrasound for fetal anatomy and growth. |
| Fertility Effects | Reversible suppression of ovulation. After discontinuation, normal fertility typically resumes within 1-3 months. Long-term use does not cause permanent infertility. |
| Food/Dietary | Avoid grapefruit juice as it may increase estrogen levels. No other significant food interactions. |
| Clinical Pearls | Monitor for thromboembolic events, especially in smokers >35 years. Counsel on strict adherence to 21-day regimen. Consider CYP3A4 inducer/inhibitor interactions. For missed pills, follow manufacturer's algorithm. Use caution in migraine with aura, hypertension, or history of DVT. |
| Patient Advice | Take one tablet daily at the same time for 21 days, then 7 pill-free days. · Missed pill: If <12 hours late, take immediately; if >12 hours, take and skip missed dose; if >2 pills missed, use backup contraception for 7 days. · Common side effects: nausea, breast tenderness, breakthrough bleeding (usually resolves). · Seek emergency care for sudden severe headache, chest pain, leg pain/swelling, vision changes, or jaundice. · Tell your doctor about all medications, especially antibiotics, antifungals, anticonvulsants, and St. John's wort. · Smoking increases risk of serious cardiovascular side effects; avoid smoking. |