OVULEN-28
Clinical safety rating
cautionComprehensive clinical and safety monograph for OVULEN-28 (OVULEN-28).
Combination estrogen-progestin oral contraceptive that inhibits ovulation primarily by suppressing gonadotropin-releasing hormone (GnRH) from the hypothalamus, reducing follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion, and altering cervical mucus and endometrial lining.
| Metabolism | Ethinyl estradiol is primarily metabolized via CYP3A4; ethynodiol diacetate undergoes extensive first-pass metabolism, converted to norethindrone and other metabolites. |
| Excretion | Renal: ~50% as metabolites; Fecal/biliary: ~40% as conjugated metabolites; <1% unchanged in urine. |
| Half-life | Ethinyl estradiol: 13-27 hours (mean ~17 hours); Norethindrone: 5-14 hours (mean ~8 hours). Clinical context: Steady state reached within 5-7 days. |
| Protein binding | Ethinyl estradiol: 98-99% bound (albumin, SHBG); Norethindrone: 80-85% bound (albumin, SHBG). |
| Volume of Distribution | Ethinyl estradiol: 2.3-3.2 L/kg (extensive tissue distribution); Norethindrone: 2.1-2.8 L/kg (distribution consistent with steroid hormones). |
| Bioavailability | Ethinyl estradiol: 38-48% (extensive first-pass metabolism); Norethindrone: 50-77% (oral bioavailability). |
| Onset of Action | Oral: Contraceptive effect begins after 7 days of continuous dosing. Ovulation suppression occurs within the first cycle. Maximal hormone levels achieved 1-2 hours post-dose. |
| Duration of Action | Contraceptive protection persists for 24 hours with daily dosing. Withdrawal bleeding typically occurs 2-3 days after last active tablet. Hormonal effects decline over 5-7 days after discontinuation. |
| Molecular Weight | 376.5 Da (ethynodiol diacetate: 384.5 Da; ethinylestradiol: 296.4 Da; combined product: average ~340 Da) |
One tablet (ethinyl estradiol 0.05 mg / ethynodiol diacetate 1 mg) orally once daily for 21 days followed by 7 days placebo; continuous cycle.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment; use with caution in severe renal impairment. |
| Liver impairment | Contraindicated in acute or chronic liver disease, including hepatic adenomas or carcinoma; discontinue if jaundice develops. |
| Pediatric use | Not indicated for use before menarche; postmenarche: same as adult dosing after assessment of bone age and growth potential. |
| Geriatric use | Not indicated for use after menopause; no specific dose adjustment, but consider increased risk of thromboembolic events and estrogen-dependent neoplasms. |
| 1st trimester | Ethinylestradiol and ethynodiol diacetate are contraindicated in pregnancy. Use during first trimester is associated with fetal harm, including cardiovascular defects and limb reduction defects. Pregnancy should be excluded before initiating therapy. |
| 2nd trimester | Contraindicated. Continued use in second trimester increases risk of fetal abnormalities and maternal complications (e.g., thromboembolism). |
| 3rd trimester | Contraindicated. Third trimester use may cause fetal adrenal suppression and maternal thrombotic events. |
Clinical note
Comprehensive clinical and safety monograph for OVULEN-28 (OVULEN-28).
| Placental transfer | Both components cross the placenta. Ethinylestradiol has been detected in fetal tissues and cord blood. Animal studies show transfer and potential teratogenicity. |
| Breastfeeding | Ethinylestradiol and ethynodiol diacetate are excreted in breast milk in small amounts. Estrogen-containing contraceptives may reduce milk production and alter milk composition, especially in early postpartum. Use is generally not recommended during breastfeeding; non-hormonal methods are preferred. |
| Lactation Rating | L4 (Hazardous) |
| Teratogenic Risk | First trimester exposure is associated with increased risk of noncardiac birth defects (e.g., limb reduction defects) and cardiac anomalies (e.g., VSD, TGA). Postnatal studies show no increased risk with second or third trimester use. Avoid use in pregnancy due to known risks. |
| Fetal Monitoring | Monitor blood pressure, glucose, and liver function. If pregnancy occurs, discontinue immediately and perform ultrasound for fetal anatomy. |
| Fertility Effects | Suppresses ovulation by inhibiting gonadotropins. Normal fertility returns upon discontinuation. No known long-term impairment. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular events (e.g., myocardial infarction, thromboembolism, stroke) from combination oral contraceptive use. Risk increases with age and heavy smoking (≥15 cigarettes/day), particularly in women over 35.
| Serious Effects |
Known or suspected pregnancyHistory of or current thromboembolic disordersCerebrovascular or coronary artery diseaseKnown or suspected breast cancerUndiagnosed abnormal genital bleedingHepatic adenoma or carcinomaActive liver disease or impaired liver functionKnown hypersensitivity to any component
| Precautions | Increased risk of thrombotic disorders (e.g., venous thromboembolism, arterial thromboembolism), cardiovascular events, hepatic neoplasia, and gallbladder disease. Discontinue if jaundice or visual disturbances occur. Monitor for hypertension, depression, and fluid retention. |
| Food/Dietary | No significant food interactions. May be taken with or without food. Grapefruit juice may increase estrogen levels; avoid excessive consumption. |
| Clinical Pearls | Ovulen-28 (ethynodiol diacetate 1 mg/mestranol 0.1 mg) is a first-generation combined oral contraceptive. Counsel patients to take at the same time daily. If a dose is missed, follow standard missed pill protocol. Drug interactions with rifampin, anticonvulsants, and certain antibiotics may reduce efficacy. Monitor for hypertension, thromboembolism, and liver dysfunction. Not recommended for smokers over 35. Assess for contraindications including history of DVT, stroke, or migraine with aura. |
| Patient Advice | Take one pill daily at the same time, even during your period. · If you miss a pill, take it as soon as you remember; if more than 12 hours late, use backup contraception. · Ovulen-28 does not protect against HIV or other STDs. · Common side effects include nausea, breast tenderness, and spotting; these usually improve. · Report symptoms of blood clots (leg pain, chest pain, sudden headache or vision changes) immediately. · Avoid smoking, especially if over 35, due to increased risk of serious side effects. · Tell your doctor about all other medications you take. · Store at room temperature away from moisture and heat. |
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