Ethinyl estradiol

Ethinyl estradiol

Systematic (IUPAC) name
19-nor-17α-pregna-1,3,5(10)-trien-20-yne-3,17-diol
Clinical data
Pronunciation	/ˌɛθᵻnᵻlˌiːstrəˈdaɪ.əl/
AHFS/Drugs.com	International Drug Names
MedlinePlus	a604032
Pregnancy category	X (USA)
Legal status	Rx-only (U.S.)
Routes of administration	Oral, transdermal
Pharmacokinetic data
Bioavailability	97% is bound
Metabolism	Liver
Biological half-life	36 ± 13 hours
Excretion	Feces and urine
Identifiers
CAS Number	57-63-6 Y
ATC code	G03CA01 (WHO) L02AA03
PubChem	CID: 5991
IUPHAR/BPS	7071
DrugBank	DB00977 Y
ChemSpider	5770 Y
UNII	423D2T571U Y
KEGG	D00554 Y
ChEBI	CHEBI:4903 Y
ChEMBL	CHEMBL691 Y
Chemical data
Formula	C20H24O2
Molecular mass	296.403 g/mol
SMILES Oc1cc4c(cc1)[C@H]3CC[C@]2([C@@H](CC[C@]2(C#C)O)[C@@H]3CC4)C
InChI InChI=1S/C20H24O2/c1-3-20(22)11-9-18-17-6-4-13-12-14(21)5-7-15(13)16(17)8-10-19(18,20)2/h1,5,7,12,16-18,21-22H,4,6,8-11H2,2H3/t16-,17-,18+,19+,20+/m1/s1 Y Key:BFPYWIDHMRZLRN-SLHNCBLASA-N Y
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Ethinyl estradiol, also sometimes written as 17α-ethinyl estradiol, ethinylestradiol, ethynyl estradiol, or ethinyl œstradiol, is a derivative of 17β-estradiol (E2), the major endogenous estrogen in humans. EE2 is an orally bioactive estrogen used in many formulations of combined oral contraceptive pills and is one of the most commonly used medications for this purpose.

Transdermal ethinyl estradiol carries a greater risk of clot formation and venous thromboembolism than naturally occurring 17β-estradiol, which some have theorized to be related to different amounts of hepatic metabolism after absorption. The same contraindications and precautions apply for EE2 as with other estrogen medications.

Estinyl was a preparation of EE2 alone that was used for the management of menopausal symptoms and female hypogonadism.

EE2 is released into the environment as a xenoestrogen from the urine and feces of people who take it as a medication.

The major concern with unopposed estrogen (without progestogen) is of endometrial cancer. As such, the medication is generally prescribed with progesterone in the setting of birth control.

History

The first orally active semisynthetic steroidal estrogen, EE2 (17α-ethynylestradiol), the 17α-ethynyl analog of E2, was synthesized in 1938 by Hans Herloff Inhoffen and Walter Hohlweg at Schering AG in Berlin.

EE2 was approved by the FDA in the U.S. on June 25, 1943 and marketed by Schering as Estinyl.

The FDA withdrew approval of Estinyl effective June 4, 2004 at the request of Schering, who had discontinued marketing Estinyl.

Pharmacology

While E2 is readily absorbed when taken orally, it is also quickly inactivated by the liver. Substitution at C17 of the estrane steroid with an ethinyl group served to provide an estrogen that is much more resistant to degradation and paved the way for the development of oral contraceptives.

EE2 is absorbed in the small intestine and reaches a serum peak about 2 hours later. It undergoes extensive metabolism in the liver involving the cytochrome P450 3A4 isoenzyme. EE2 and its metabolites are excreted with the bile. Due to the effect of enterohepatic circulation a second peak is seen several hours later. Individually, wide variations exist in the overall absorption process, and can be further modified by drugs (i.e. antibiotics) that affect the enterohepatic circulation or liver enzymes. In circulation EE2 is almost fully bound to plasma albumin. It is metabolized by hydroxylation of the aromatic ring and excreted in both feces and urine, in part as glucuronide and sulfate conjugate.

EE2 is hormonally effective by activating the estrogen receptor and thus is an estrogen. It finds its most common use in the estrogen-progestin combination preparations of oral contraceptives. Over time, formulations have decreased the EE2 dose from as high as 100 μg to as low as 10 μg in LoLoestrin Fe.

See also

• Methyl estradiol
• Mestranol
• Hormonal contraception
• Oral contraceptive formulations
• Birth Control
• Hormone replacement therapy
• Diethylstilbestrol
• Estrogen ester

External links

• Drugs.com - Ethinyl Estradiol Side Effects