NORGESTIMATE; ETHINYL ESTRADIOL
Clinical safety rating: avoid
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Combination oral contraceptive containing norgestimate (a progestin) and ethinyl estradiol (an estrogen). The primary mechanism is suppression of gonadotropins (FSH and LH) via negative feedback on the hypothalamic-pituitary-ovarian axis, preventing ovulation. Additional effects include thickening cervical mucus (inhibiting sperm penetration) and altering endometrial receptivity.
| Metabolism | Norgestimate is extensively metabolized via first-pass metabolism in the liver, primarily to norelgestromin (active metabolite) and further to levonorgestrel. Ethinyl estradiol is metabolized via CYP3A4 in the liver and undergoes conjugation. Both undergo enterohepatic recirculation. |
| Excretion | Norgestimate metabolites are primarily excreted via urine (60-80%) and feces (35-49%) as glucuronide and sulfate conjugates; ethinyl estradiol is excreted in urine (40%) and feces (60%) as conjugates. |
| Half-life | Norgestimate: terminal half-life of norelgestromin (active metabolite) is 27.6 ± 7.8 hours; ethinyl estradiol: terminal half-life is 17.5 ± 6.3 hours. Steady state achieved within 14 days. |
| Protein binding | Norelgestromin: 99% bound primarily to albumin, less to SHBG; norgestrel (minor metabolite): 99% bound; ethinyl estradiol: 97-98% bound, mainly to albumin, with 20-30% binding to SHBG. |
| Volume of Distribution | Norelgestromin: 2.0-2.3 L/kg (large, indicating extensive tissue distribution); ethinyl estradiol: 2.3-3.8 L/kg (large, distributed to tissues). |
| Bioavailability | Oral: norgestimate is rapidly and completely absorbed, undergoes first-pass metabolism to active norelgestromin (bioavailability ≈ 60-70%); ethinyl estradiol bioavailability is 40-50% due to first-pass metabolism. |
| Onset of Action | Oral: contraceptive effect begins after 7 days of continuous use if started on day 1 of menstrual cycle; if started otherwise, additional contraception needed for 7 days. |
| Duration of Action | Oral: contraceptive protection lasts 24 hours per daily dose; hormone levels return to baseline within 5-7 days after discontinuation for norgestimate metabolites, 3-5 days for ethinyl estradiol. |
| Molecular Weight | Norgestimate: 369.5 Da; Ethinyl estradiol: 296.4 Da (combination product: norgestimate/ethinyl estradiol) |
Oral, one tablet daily at the same time for 21 days, followed by 7 placebo tablets.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for GFR >= 30 mL/min; use is not recommended in patients with severe renal impairment (GFR < 30 mL/min). |
| Liver impairment | Contraindicated in severe hepatic disease (Child-Pugh class C). In mild to moderate disease (Child-Pugh class A or B), use with caution and monitor for adverse effects; no specific dose adjustment guidelines established. |
| Pediatric use | No FDA-approved indication in pediatric patients. Use is generally not recommended before menarche. |
| Geriatric use | Not indicated for postmenopausal women. No dose adjustment required in elderly women of reproductive age, but consider increased risk of thromboembolism and cardiovascular events. |
| 1st trimester | Avoid during first trimester unless benefit outweighs risk; oral contraception formulations containing estrogens and progestins are not indicated for use during pregnancy and carry theoretical risk of teratogenicity, though large population studies have not consistently shown increased risk of birth defects. |
| 2nd trimester | Avoid use during second trimester; not indicated for pregnancy and fetal exposure may affect development. No established safety data. |
| 3rd trimester | Avoid use during third trimester; may cause adverse effects in the neonate including withdrawal bleeding, jaundice, and potential estrogenic effects. Not indicated during pregnancy. |
Clinical note
Inducers of CYP450 enzymes (eg carbamazepine) may decrease estrogen levels Increases risk of thromboembolic disorders and endometrial cancer.
| Placental transfer | Both norgestimate and ethinyl estradiol cross the placenta. Norgestimate is extensively metabolized to active metabolites (e.g., norelgestromin) which are detectable in fetal circulation. Ethinyl estradiol also demonstrates placental transfer with fetal serum levels approximately 5-10% of maternal levels. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular adverse events from combination oral contraceptives. The risk increases with age and heavy smoking (≥15 cigarettes per day) and is substantial in women over 35 years of age. Women who use combination hormonal contraceptives should be strongly advised not to smoke.
| Common Effects | Headache Dizziness Breast tenderness Nausea Vaginal spotting Vomiting Abdominal cramp |
| Serious Effects |
Current or history of thrombophlebitis or thromboembolic disordersHistory of deep vein thrombosis or pulmonary embolismCerebrovascular or coronary artery diseaseKnown or suspected pregnancyCurrent or past breast cancer or other estrogen-sensitive neoplasiaUndiagnosed abnormal uterine bleedingHepatic adenoma or carcinoma, or active liver disease with abnormal liver functionKnown or suspected pregnancyMajor surgery with prolonged immobilizationDiabetes mellitus with vascular involvementUncontrolled hypertensionMigraine with focal neurological symptoms (especially in women over 35)Smoking in women over 35 years of age (if using combined hormonal contraception)
| Precautions |
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| Breastfeeding | Norgestimate and ethinyl estradiol are excreted in human breast milk in small amounts. Use during breastfeeding may reduce milk production and quantity, and may pass to the infant. Caution is advised, and alternative methods of contraception should be considered for breastfeeding women, especially in the early postpartum period. |
| Lactation Rating | L3 - Moderately Safe (avoid if possible, especially in first 6 weeks postpartum due to potential milk suppression) |
| Teratogenic Risk | First trimester: Limited data, no consistent evidence of major malformations from inadvertent exposure. Second and third trimesters: May increase risk of adverse fetal outcomes including cardiovascular malformations, preterm birth, low birth weight. Avoid use during pregnancy. |
| Fetal Monitoring | Monitor blood pressure, signs of thrombosis, and liver function. In pregnancy: assess fetal growth via ultrasound if inadvertent exposure occurs. |
| Fertility Effects | Suppresses ovulation via inhibition of gonadotropins. Fertility returns to normal upon discontinuation. No long-term impairment. |
| Thromboembolic disorders: Increased risk of venous thromboembolism (VTE) and arterial thromboembolism (ATE). Discontinue if thrombotic events occur., Cardiovascular disease: Increased risk of myocardial infarction and stroke, especially in smokers and women over 35., Cervical cancer: Increased risk of cervical intraepithelial neoplasia; monitor for abnormal bleeding., Liver disease: Discontinue if jaundice, cholestasis, or other liver dysfunction develops., Hypertension: May cause or worsen hypertension; monitor blood pressure regularly., Carbohydrate metabolism: May impair glucose tolerance; monitor diabetic patients., Headache: May exacerbate migraine; discontinue if new or severe headache occurs., Unscheduled bleeding: May occur, especially during first few cycles., Depression: May worsen or cause depression; discontinue if severe. |
| Food/Dietary | No significant food interactions. Grapefruit juice may slightly increase ethinyl estradiol levels but is not considered clinically significant. Avoid St. John's wort as it can reduce contraceptive efficacy. |
| Clinical Pearls | Norgestimate/ethinyl estradiol is a combination oral contraceptive with a progestin structurally similar to levonorgestrel. It is often associated with a lower incidence of androgenic side effects such as acne and hirsutism. Use with caution in women with migraine with aura due to increased stroke risk. The typical regimen is 21 active pills followed by 7 placebo pills; missed pills increase pregnancy risk and require backup contraception. Breakthrough bleeding is common in the first few cycles and usually resolves. Do not prescribe to smokers over 35 years old due to thromboembolic risk. |
| Patient Advice | Take one pill at the same time every day, even if you do not have sex, for maximum effectiveness. · If you miss a pill, follow the package instructions: if >48 hours, use backup contraception for 7 days. · This medication does not protect against sexually transmitted infections (STIs); use condoms for STI prevention. · Common side effects may include nausea, breast tenderness, and breakthrough bleeding, especially during the first 3 months. · Smoking increases your risk of serious cardiovascular side effects; do not smoke while taking this medication, especially if over 35. · Notify your doctor immediately if you experience sudden severe headache, chest pain, shortness of breath, leg pain or swelling, vision changes, or jaundice. |