OVULEN
Clinical safety rating
cautionComprehensive clinical and safety monograph for OVULEN (OVULEN).
Ovulen is a combination oral contraceptive containing ethynodiol diacetate (a progestin) and mestranol (an estrogen). It inhibits ovulation by suppressing gonadotropin-releasing hormone (GnRH) from the hypothalamus, reducing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion from the pituitary. It also increases cervical mucus viscosity and alters endometrial development, impeding sperm penetration and implantation.
| Metabolism | Ethynodiol diacetate is rapidly metabolized to norethindrone, primarily via hydrolysis, then undergoes reduction, hydroxylation, and conjugation. Mestranol is metabolized to ethinyl estradiol via demethylation, followed by further hydroxylation and conjugation. Both are metabolized by cytochrome P450 enzymes, including CYP3A4. |
| Excretion | Renal: 50-60% as metabolites (glucuronide and sulfate conjugates), biliary/fecal: 40-50% (enterohepatic circulation). |
| Half-life | Ethinylestradiol: 10-20 hours (mean 17 hours); Dimethisterone: 10-15 hours. Clinical context: Steady state achieved after 3-5 days; elimination prolonged in hepatic impairment. |
| Protein binding | Ethinylestradiol: 97-98% bound to albumin and sex hormone-binding globulin (SHBG); Dimethisterone: ~90% bound to albumin and SHBG. |
| Volume of Distribution | Ethinylestradiol: 2-4 L/kg (large Vd indicating extensive tissue distribution, including reproductive tissues and fat); Dimethisterone: 1.5-2.5 L/kg. |
| Bioavailability | Oral: Ethinylestradiol 40-60% (first-pass metabolism); Dimethisterone ~70% (oral bioavailability). |
| Onset of Action | Oral: Onset of contraceptive effect after 7 days of continuous dosing; therapeutic effect for cycle control within first cycle. |
| Duration of Action | Oral: Contraceptive protection lasts 24 hours; once-daily dosing required. Withdrawal bleeding occurs 2-3 days after last active pill. |
| Molecular Weight | 378.55 |
1 tablet (1 mg ethynodiol diacetate, 50 mcg mestranol) orally once daily for 21 days, followed by 7 days of placebo or no medication.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment guidelines available; use caution in severe renal impairment (CrCl <30 mL/min) due to potential hormonal accumulation. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). In mild to moderate impairment (Child-Pugh A or B), use with caution; no specific dose reduction established. |
| Pediatric use | Approved only for postmenarchal adolescents; same dosing as adults (1 tablet daily for 21 days with 7-day break). Not indicated before menarche. |
| Geriatric use | Not indicated for use in postmenopausal women. Efficacy and safety in elderly (age >65 years) have not been established. |
| 1st trimester | Contraindicated due to increased risk of cardiovascular and birth defects (e.g., VACTERL syndrome) from estrogen-progestin exposure, primarily through off-label use for contraception. |
| 2nd trimester | Contraindicated; may cause fetal harm, including masculinization of female fetuses from progestin component. |
| 3rd trimester | Contraindicated; risk of feminization of male fetuses and other endocrine effects. |
Clinical note
Comprehensive clinical and safety monograph for OVULEN (OVULEN).
| Placental transfer | Crosses placenta; documented transfer of ethinylestradiol and ethynodiol diacetate in animal and human studies. |
| Breastfeeding | Excreted in breast milk; may reduce milk production and quality. Use only if benefits outweigh risks, and monitor infant for jaundice, weight gain, and estrogenic effects. |
| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | FDA Pregnancy Category X. Contraindicated in pregnancy due to risk of fetal harm, including cardiovascular anomalies and limb defects. First trimester exposure associated with major congenital malformations; second and third trimester exposure may cause feminization of male fetuses. |
| Fetal Monitoring | Baseline pregnancy test before initiating; monitor for signs of thromboembolism, hypertension, and hepatic dysfunction. Fetal ultrasound if inadvertent exposure occurs. |
| Fertility Effects | Suppresses ovulation; after discontinuation, return to fertility may be delayed for 1–3 months. No evidence of permanent impairment. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular events from combination oral contraceptive use. The risk increases with age, especially in women over 35 years, and with the number of cigarettes smoked. Women who use combination oral contraceptives should be strongly advised not to smoke.
| Serious Effects |
Thromboembolic disordersKnown or suspected pregnancyBreast cancer (current or history)Estrogen-dependent neoplasiaUndiagnosed abnormal genital bleedingHepatic adenoma or carcinomaSevere liver disease (e.g., acute hepatitis, decompensated cirrhosis)Jaundice with prior pill useActive thrombophlebitisHypertriglyceridemia (marked)Known hypersensitivity to components
| Precautions | Cigarette smoking increases risk of cardiovascular events; avoid in women over 35 who smoke., Increased risk of thromboembolic disorders (e.g., deep vein thrombosis, pulmonary embolism, stroke, myocardial infarction). Discontinue if thrombotic events occur or are suspected., Elevated blood pressure; monitor regularly., Gallbladder disease; may worsen or precipitate., Hepatic neoplasia; rare cases of benign and malignant liver tumors reported., Carcinoma of breast and reproductive organs; increased risk with long-term use; monitor if history., Ocular lesions; discontinue if sudden partial or complete loss of vision, proptosis, diplopia, or papilledema occurs., Glucose intolerance; use with caution in diabetics., Unscheduled bleeding; rule out pregnancy or other causes., Depression; discontinue if severe or recurrent. |
| Food/Dietary | No significant food interactions. Grapefruit juice may alter estrogen metabolism but clinical relevance is minimal. Maintain regular diet; no restrictions. |
| Clinical Pearls | Ovulen (ethynodiol diacetate 1 mg + mestranol 0.1 mg) is a first-generation combined oral contraceptive. Monitor for thromboembolic events, especially in smokers over 35. Use with caution in patients with hypertension, migraine with aura, or liver disease. Breakthrough bleeding is common in the first 3 cycles. |
| Patient Advice | Take one pill daily at the same time, even if no sexual activity. · Use backup contraception (e.g., condoms) for the first 7 days of starting the pill. · Report sudden severe headache, chest pain, leg swelling, or vision changes immediately. · Smoking increases risk of serious cardiovascular side effects; avoid smoking. · Missed pills increase pregnancy risk; follow missed pill instructions in the patient leaflet. |
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