ESTINYL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ESTINYL (ESTINYL).
Estinyl (ethinyl estradiol) is a synthetic estrogen that binds to estrogen receptors, leading to increased synthesis of DNA, RNA, and various proteins in target tissues. It suppresses gonadotropin release, modulating the hypothalamic-pituitary-ovarian axis.
| Metabolism | Primarily hepatic via CYP3A4; undergoes first-pass metabolism; conjugates with glucuronic acid and sulfate; enterohepatic recirculation occurs. |
| Excretion | Renal excretion of metabolites (approximately 40-50% as ethinyl estradiol glucuronide and sulfate conjugates) and fecal excretion (approximately 20-30% as conjugates and minor metabolites); <10% excreted unchanged in urine. |
| Half-life | Terminal elimination half-life is approximately 13-27 hours (mean ~17 hours); enterohepatic recirculation contributes to variability; steady-state achieved within 3-5 days. |
| Protein binding | Highly bound to serum albumin (~97-98%); also binds to sex hormone-binding globulin (SHBG) with lower affinity. |
| Volume of Distribution | Apparent volume of distribution is approximately 2.5-5.5 L/kg (mean ~3 L/kg), indicating extensive extravascular distribution and tissue binding. |
| Bioavailability | Oral bioavailability is approximately 40-45% due to first-pass metabolism in the gut wall and liver; substantial interindividual variability (range 20-65%). |
| Onset of Action | Oral: Onset of clinical effect (e.g., contraceptive efficacy) occurs within 3-7 days of initiation; effects on endometrium and pituitary-ovarian axis require continuous dosing. |
| Duration of Action | Duration of action persists for 24 hours with daily dosing; contraceptive protection is maintained with consistent daily intake; after discontinuation, ovulation may resume within 2-3 weeks. |
0.01-0.05 mg orally once daily for contraception or 2.5-10 mg orally 3-4 times daily for 5-10 days for hemostasis in dysfunctional uterine bleeding. Route: oral. Frequency: daily for contraception; multiple daily doses for acute bleeding.
| Dosage form | TABLET |
| Renal impairment | No specific GFR-based dose adjustments are established. Use with caution in patients with renal impairment due to potential fluid retention. |
| Liver impairment | Contraindicated in severe hepatic disease (Child-Pugh class C). In mild to moderate impairment (Child-Pugh A or B), use with caution and reduce dose by 50% if necessary. |
| Pediatric use | For contraception in postmenarchal adolescents: same as adult dosing (0.01-0.05 mg orally once daily). For other indications, use lowest effective dose; no standard weight-based guidelines available. |
| Geriatric use | Not typically indicated for postmenopausal women. If used, start at lowest effective dose due to increased risk of thromboembolism, fluid retention, and cardiovascular events. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ESTINYL (ESTINYL).
| Breastfeeding | Contraindicated in breastfeeding. Estrogens are excreted in breast milk with an M/P ratio of approximately 0.5-0.7. Potential for reduced milk production and adverse effects in nursing infants. Alternative contraception recommended. |
| Teratogenic Risk | FDA Pregnancy Category X. First trimester: Increased risk of congenital anomalies including cardiovascular and limb defects from estrogenic effects. Second and third trimesters: Associated with fetal harm (urogenital abnormalities, vaginal adenosis, clear cell adenocarcinoma in female offspring) due to diethylstilbestrol (DES) component. Contraindicated in pregnancy. |
■ FDA Black Box Warning
Cigarette smoking increases the risk of serious cardiovascular side effects from estrogen-containing products. 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 taking estrogens should not smoke.
| Serious Effects |
Known or suspected pregnancy; undiagnosed abnormal genital bleeding; known or suspected breast cancer (except appropriate selected cases); known or suspected estrogen-dependent neoplasia; active thromboembolic disorders or history; liver disease or impaired liver function; hypersensitivity to ethinyl estradiol; smoking in women over 35 (relative contraindication).
| Precautions | Increased risk of thromboembolic disorders, myocardial infarction, stroke, hepatic adenoma, gallbladder disease, hypertension, hypercalcemia in breast cancer patients; potential for fluid retention; glucose intolerance; worsening of endometriosis; uterine leiomyoma growth; hereditary angioedema; cholestatic jaundice; lactation suppression. |
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| Fetal Monitoring | Prior to initiation: Exclude pregnancy with sensitive test. During use: Monitor for thrombotic events (DVT, PE), hypertension, hepatic dysfunction, and glucose intolerance. Fetal monitoring not indicated as drug is contraindicated in pregnancy. Perform pregnancy test if pregnancy suspected. |
| Fertility Effects | Used for hormone replacement in hypogonadism to induce puberty and fertility. High doses may suppress ovulation and endometrial development. Reversible effect on fertility upon discontinuation. |