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Etinestryl: Full Drug Profile

Medically reviewed by Min Clinic Staff | Updated: January 2026

Etinestryl - General Information

A semisynthetic alkylated estradiol with a 17-alpha-ethinyl substitution. It has high estrogenic potency when administered orally, and is often used as the estrogenic component in oral contraceptives. [PubChem]

 

Pharmacology of Etinestryl

Ethinyl estradiol is a synthetic derivative of the natural estrogen estradiol. It is one of two estrogens currently used in oral contraceptive pills. The other, mestranol, is converted to ethinyl estradiol before it is biologically active. Ethinyl estradiol and norethindrone are used together as an oral contraceptive agent.

 

Etinestryl for patients

PATIENT PACKAGE INSERT

Vaginal Cream, Oral Tablets, and Transdermal System

This information describes when and how to use estrogens, and the risks and benefits of estrogen treatment.

Estrogens have important benefits but also some risks. You must decide, with your doctor, whether the risks to you of estrogen use are acceptable because of their benefits. If you use estrogens, check with your doctor to be sure you are using the lowest possible dose that works, and that you don't use them longer than necessary. How long you need to use estrogens will depend on the reason for use.

Additional Information for the Climara System: The Climara system that your doctor has prescribed for you releases small amounts of estradiol through the skin in a continuous way. Estradiol is the same hormone that your ovaries produce abundantly before menopause. The dose of estradiol you require will depend upon your individual response. The dose is adjusted by the size of the Climara system used: the systems are avaialble in 4 sizes.

 

Etinestryl Interactions

Certain endocrine and liver function tests may be affected by estrogen-containing oral contraceptives. The following similar changes may be expected with larger doses of estrogen:

Increased sulfobromophthalein retention; increased prothrombin and factors VII, VIII, IX, and X; decreased antithrombin 3; increased norepinephrine-induced platel et aggregation; increased thyroid binding globulin (TBG) leading to increased circulating total thyroid hormone, as measured by PBI, T4 by column, or T4 by radioimmunoassay. Free T3 resin uptake is decreased, reflecting the elevated TBG; free T4 concentration is unaltered: impaired glucose tolerance; decreased pregnanediol excretion; reduced response to metyrapone test; reduced serum folate concentration; increased serum triglyceride and phospholipid concentration.

 

Etinestryl Contraindications

Estrogens should not be used in women (or men) with any of the following conditions:

1. Known or suspected cancer of the breast except in appropriately selected patients being treated for metastatic disease.

2. Known or suspected estrogen-dependent neoplasia.

3. Known or suspected pregnancy.

4. Undiagnosed abnormal genital bleeding.

5. Active thrombophlebitis or thromboembolic disorders.

6. A past history of thrombophlebitis, thrombosis, or thromboembolic disorders associated with previous estrogen use (except when used in treatment of breast or prostatic malignancy).

 

Additional information about Etinestryl

Etinestryl Indication

For treatment of moderate to severe vasomotor symptoms associated with the menopause, female hypogonadism, prostatic carcinoma-palliative therapy of advanced disease, breast cancer, as an oral contraceptive, and as emergency contraceptive.

Mechanism Of Action
Estrogens diffuse into their target cells and interact with a protein receptor. Target cells include the female reproductive tract, the mammary gland, the hypothalamus, and the pituitary. Estrogens increase the hepatic synthesis of sex hormone binding globulin (SHBG), thyroid-binding globulin (TBG), and other serum proteins and suppress follicle-stimulating hormone (FSH) from the anterior pituitary. The combination of an estrogen with a progestin suppresses the hypothalamic-pituitary system, decreasing the secretion of gonadotropin-releasing hormone (GnRH).
Drug Interactions
Aminophylline The contraceptive increases the effect and toxicity of theophylline
Generic Name
Ethinyl Estradiol
Synonyms
Ethinylestradiolum [Inn-Latin]; Ethinyl-Oestranol; Ethinylestriol; Ethinyloestradiol; Ethynylestradiol; Ethynyloestradiol; Etinilestradiol [Inn-Spanish]; EE; EO; Aethinyoestradiol [German]; 17 alpha-Ethinylestradiol; Aethinyloestradiolum; 17 alpha-Ethynyloestradiol; 17 alpha-Ethynylestradiol
Drug Category
Estrogens
Drug Type
Small Molecule; Approved
Other Brand Names containing Ethinyl Estradiol
Amenoron; Amenorone; Anovlar; Cyclosa; Dicromil; Diognat-E; Diogyn E; Diogyn-E; Diprol; Dyloform; Ertonyl; Esteed; Estigyn; Eston-E; Estopherol; Estoral; Estorals; Ethidol; Ethinoral; Ethy 11; Eticyclin; Eticyclol; Eticylol; Etinestrol; Etinestryl; Etinoestryl; Etistradiol; Etivex; Follicoral; Ginestrene; Gynolett; Halodrin; Inestra; Kolpolyn; Linoral; Marvelon; Menolyn; Mercilon; Microfollin; Neo-Estrone; Nogest-S; Novestrol; Oradiol; Orestralyn; Orestrayln; Ortho-Cyclen; Oviol; Primogyn; Primogyn C; Primogyn M; Progynon C; Progynon M; Prosexol; Spanestrin; Varnoline; Ylestrol;
Absorption
Rapid and complete absorption follows oral intake of ethinyl estradiol (bioavailability 43%).
Toxicity (Overdose)
Oral, mouse LD50: 1737 mg/kg. Symptoms of overdose include nausea and vomiting, and withdrawal bleeding may occur in females.
Protein Binding
97%
Biotransformation
Hepatic. Quantitatively, the major metabolic pathway for ethinyl estradiol, both in rats and in humans, is aromatic hydroxylation, as it is for the natural estrogens.
Half Life
36 +/- 13 hours
Dosage Forms of Etinestryl
Tablet Oral
Chemical IUPAC Name
(8R,9S,13S,14S,17R)-17-ethynyl-13-methyl-7,8,9,11,12,14,15,16-octahydro-6H-cyclopenta[a]phenanthrene-3,17-diol
Chemical Formula
C20H24O2
Organisms Affected
Humans and other mammals