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2 APIs, 1 Intermediates

2 APIs
1 Intermediates

Chemistry

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Also known as: Beta-estradiol, 17beta-estradiol, 50-28-2, Oestradiol, Dihydrofolliculin, Estrace

Molecular Formula

C₁₈H₂₄O₂

Molecular Weight

272.4 g/mol

InChI Key

VOXZDWNPVJITMN-ZBRFXRBCSA-N

FDA UNII

4TI98Z838E

The 17-beta-isomer of estradiol, an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position. Estradiol-17-beta is the most potent form of mammalian estrogenic steroids.

Estradiol is an Estrogen. The mechanism of action of estradiol is as an Estrogen Receptor Agonist.

1 2D Structure

CAS 50-28-2

2 Identification

2.1 Computed Descriptors

2.1.1 IUPAC Name

(8R,9S,13S,14S,17S)-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,17-diol

2.1.2 InChI

InChI=1S/C18H24O2/c1-18-9-8-14-13-5-3-12(19)10-11(13)2-4-15(14)16(18)6-7-17(18)20/h3,5,10,14-17,19-20H,2,4,6-9H2,1H3/t14-,15-,16+,17+,18+/m1/s1

2.1.3 InChI Key

VOXZDWNPVJITMN-ZBRFXRBCSA-N

2.1.4 Canonical SMILES

CC12CCC3C(C1CCC2O)CCC4=C3C=CC(=C4)O

2.1.5 Isomeric SMILES

C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@@H]2O)CCC4=C3C=CC(=C4)O

2.2 Other Identifiers

2.2.1 UNII

4TI98Z838E

2.3 Synonyms

2.3.1 MeSH Synonyms

1. 17 Beta Estradiol

2. 17 Beta Oestradiol

3. 17 Beta-estradiol

4. 17 Beta-oestradiol

5. Aerodiol

6. Delestrogen

7. Estrace

8. Estraderm Tts

9. Estradiol 17 Alpha

10. Estradiol 17 Beta

11. Estradiol 17beta

12. Estradiol Anhydrous

13. Estradiol Hemihydrate

14. Estradiol Hemihydrate, (17 Alpha)-isomer

15. Estradiol Monohydrate

16. Estradiol Valerate

17. Estradiol Valeriante

18. Estradiol, (+-)-isomer

19. Estradiol, (-)-isomer

20. Estradiol, (16 Alpha,17 Alpha)-isomer

21. Estradiol, (16 Alpha,17 Beta)-isomer

22. Estradiol, (17-alpha)-isomer

23. Estradiol, (8 Alpha,17 Beta)-(+-)-isomer

24. Estradiol, (8 Alpha,17 Beta)-isomer

25. Estradiol, (9 Beta,17 Alpha)-isomer

26. Estradiol, (9 Beta,17 Beta)-isomer

27. Estradiol, Monosodium Salt

28. Estradiol, Sodium Salt

29. Estradiol-17 Alpha

30. Estradiol-17 Beta

31. Estradiol-17beta

32. Oestradiol

33. Ovocyclin

34. Progynon Depot

35. Progynon-depot

36. Progynova

37. Vivelle

2.3.2 Depositor-Supplied Synonyms

1. Beta-estradiol

2. 17beta-estradiol

3. 50-28-2

4. Oestradiol

5. Dihydrofolliculin

6. Estrace

7. Vivelle

8. Ovocyclin

9. Progynon

10. Dihydrotheelin

11. Dihydroxyestrin

12. Aquadiol

13. Climara

14. Diogynets

15. Divigel

16. Gynergon

17. Gynoestryl

18. Vagifem

19. Diogyn

20. Oestroglandol

21. Aerodiol

22. Corpagen

23. Dimenformon

24. Estraderm

25. Estrogel

26. Estrovite

27. Femestral

28. Follicyclin

29. Ginosedol

30. Macrodiol

31. Oestergon

32. Ovahormon

33. Ovasterol

34. Ovastevol

35. Perlatanol

36. Primofol

37. Profoliol

38. Altrad

39. Bardiol

40. Evorel

41. Femogen

42. Lamdiol

43. Syndiol

44. Dihydromenformon

45. Estradiol-17beta

46. Cis-estradiol

47. Estraderm Tts

48. Estraldine

49. Estroclim

50. Trocosone

51. Estring

52. Menorest

53. Nordicol

54. Zumenon

55. Systen

56. D-oestradiol

57. D-estradiol

58. Progynon Dh

59. Climaderm

60. Compudose

61. Dermestril

62. Estrasorb

63. Ovocycline

64. Encore

65. Innofem

66. Menest

67. Oesclim

68. Alora

69. Dihydroxyoestrin

70. 17beta-oestradiol

71. Sk-estrogens

72. Progynon-dh

73. Fempatch

74. Gynestrel

75. Gynodiol

76. Microdiol

77. Oestrogynal

78. Ovociclina

79. Ovocylin

80. Tradelia

81. Esclim

82. Estroclim 50

83. Macrol

84. Zerella

85. Oestradiol R

86. Estring Vaginal Ring

87. Dihydrofollicular Hormone

88. Trial Sat

89. Theelin, Dihydro-

90. Elestrin

91. Evamist

92. Oestrogel

93. Compudose 200

94. Compudose 365

95. Profoliol B

96. 17b-oestradiol

97. 17-beta-estradiol

98. Estradiol-17-beta

99. Estradot

100. Estrogen

101. Gelestra

102. Menostar

103. 3,17-epidihydroxyestratriene

104. Zesteem

105. Dihydroxyesterin

106. Cis-oestradiol

107. Estraderm Tts 50

108. Estrogens, Esterified

109. Nsc-9895

110. 17.beta.-estradiol

111. B-estradiol

112. Epiestriol 50

113. 17beta Oestradiol

114. 17 Beta-estradiol

115. Estradiol-17 Beta

116. Amnestrogen

117. Femanest

118. Estra-1,3,5(10)-triene-3,17beta-diol

119. 3,17-epidihydroxyoestratriene

120. Sandrena 1

121. 17b-estradiol

122. (17beta)-estra-1,3,5(10)-triene-3,17-diol

123. Estraderm (tn)

124. Estradiol Anhydrous

125. [3h]-estradiol

126. 17

127. A-estradiol

128. 17

129. A-oestradiol

130. Estrogel (tn)

131. Climara (tn)

132. Divigel (tn)

133. Estrace (tn)

134. Estring (tn)

135. Innofem (tn)

136. Vagifem (tn)

137. Vivelle (tn)

138. 17.beta.-oestradiol

139. Elestrim

140. 3,17.beta.-estradiol

141. .beta.-estradiol

142. (8r,9s,13s,14s,17s)-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,17-diol

143. .beta.-oestradiol

144. [3h]]estradiol

145. Estradiol 17-beta

146. 17-beta-oestradiol

147. Estradiol, .beta.-

148. Estradiol-17.beta.

149. Chebi:16469

150. Estra-1,3,5(10)-triene-3,17-diol (17beta)-

151. Oestradiol-17.beta.

152. 17-.beta.-oestradiol

153. Estradiol Hemihydrate

154. Oestra-1,3,5(10)-triene-3,17beta-diol

155. Estrasorb (tn)

156. 17.beta.-oh-estradiol

157. 17.beta.-oh-oestradiol

158. 17beta Estradiol (e2)

159. Extrasorb

160. 17beta-estra-1,3,5(10)-triene-3,17-diol

161. Estreva

162. Estrifam

163. Femtran

164. Ginedisc

165. Nsc-20293

166. Chembl135

167. Gynpolar

168. (17beta)-estra-1(10),2,4-triene-3,17-diol

169. Sandrena Gel

170. D-3,17.beta.-estradiol

171. D-3,17.beta.-oestradiol

172. Sisare Gel

173. Estra-1,3,5(10)-triene-3,17-diol, (17beta)-

174. Estrofem 2

175. Mls000069494

176. 3,17b-dihydroxyestra-1,3,5(10)-triene

177. (+)-3,17.beta.-estradiol

178. 141290-02-0

179. Oestradiolum

180. Estradiol Valerate Metabolite E2

181. Climara Forte

182. 4ti98z838e

183. Oestradiol Berco

184. Estraderm Mx

185. Vivelle-dot

186. [3h]e2

187. Wc3011

188. Oestradiol-17beta

189. Estrapak 50

190. (1s,10r,11s,14s,15s)-15-methyltetracyclo[8.7.0.0^{2,7}.0^{11,15}]heptadeca-2(7),3,5-triene-5,14-diol

191. (8r,9s,13s,14s,17s)-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6h-cyclopenta[a]phenanthrene-3,17-diol

192. E2

193. Wc-3011

194. Estradiolum [inn]

195. Estradiolo [dcit]

196. Ncgc00091544-04

197. Oestradiol-17-beta

198. Estradiolum

199. Estrodiolum

200. Estradiolo

201. Femestrol

202. Smr000059126

203. Estradiol-3,17beta

204. Dsstox_cid_573

205. 17-beta-oh-estradiol

206. 3,17-beta-estradiol

207. 3,17beta-dihydroxyestra-1,3,5(10)-triene

208. 3,17-beta-oestradiol

209. D-3,17beta-estradiol

210. Estra-1,3,5(10)-triene-3,17.beta.-diol

211. 3,17.beta.-dihydroxyestra-1,3,5(10)-triene

212. E(sub 2)

213. Dsstox_rid_75666

214. Methyl 1-cyclopropyl-6,7-difluoro-8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylate.

215. Benzogynestry

216. Dsstox_gsid_20573

217. Estropause

218. Estasorb

219. [2,4,6,7-3h]-e2

220. E 2

221. Destradiol

222. Minivelle

223. Yuvvexy

224. Zesteen

225. .alpha.-estradiol

226. 17-beta-oh-oestradiol

227. 17?-estradiol

228. D-3,17beta-oestradiol

229. D-3,17-beta-estradiol

230. Estrodiolum [inn-latin]

231. Estra-1,3,5(10)-triene-3,17-diol (17.beta.)-

232. D-3,17-beta-oestradiol

233. Activella (salt/mix)

234. Combipatch (salt/mix)

235. Ccris 280

236. Component Of Menrium

237. Estradiol-17 Alpha

238. Climara Pro (salt/mix)

239. 3,17beta-estradiol

240. 3,17-.beta.-oestradiol

241. Estraderm Tts 100

242. Hsdb 3589

243. 3,3,5(10)-triene

244. Sr-01000075866

245. 17-.beta.-estradiol

246. Einecs 200-023-8

247. 1,3,5-estratriene-3,17-beta-diol

248. Oestrodiol

249. Estradiol [usp:inn:ban]

250. 3,17beta-dihydroxyestra-1,3,5-triene

251. 3,17beta-dihydroxyoestra-1,3,5-triene

252. Delta-estradiol

253. Dihydro-theelin

254. 3,17-beta-dihydroxyoestra-1,3,5-triene

255. Unii-4ti98z838e

256. Beta -estradiol

257. Delta-oestradiol

258. Tx-004hr

259. Estra-1,3,5(10)-triene-3,17-beta-diol

260. Estradiol Complex

261. Estrogel Hbf

262. Oestra-1,3,5(10)-triene-3,17-beta-diol

263. 1jgl

264. 1lhu

265. 1qkt

266. 1qku

267. 3,17-beta-dihydroxyestra-1,3,5(10)-triene

268. [3h]estradiol

269. 1,3,5-estratriene-3,17.beta.-diol

270. 3,17-beta-dihydroxy-1,3,5(10)-oestratriene

271. Cas-50-28-2

272. 17-beta-estra-1,3,5(10)-triene-3,17-diol

273. 17beta-oestra-1,3,5(10)-triene-3,17-diol

274. .alpha.-oestradiol

275. 17-beta-oestra-1,3,5(10)-triene-3,17-diol

276. Estra-1,3,5(10)-triene-3,17-diol

277. Prestwick_207

278. 3,17b-estradiol

279. Bio-e-gel

280. Fem7

281. [3h]-estrogen

282. 17 ?-estradiol

283. 3,17.beta.-dihydroxyestra-1,3,5-triene

284. 3,17.beta.-dihydroxyoestra-1,3,5-triene

285. Cmc_11154

286. Imvexxy

287. 1,3,5,(10)-estratrien-3,17.beta.-diol

288. Sl-1100

289. Oestra-1,3,5(10)-triene-3,17.beta.-diol

290. 2j7x

291. 3,17.beta.-dihydroxy-1,3,5(10)-estratriene

292. 3,17.beta.-dihydroxy-1,3,5(10)-oestratriene

293. 3,3,5-triene

294. [3h]17beta-estradiol

295. Estradiol [inn]

296. Estradiol [jan]

297. (17?)-estra-1,3,5(10)-triene-3,17-diol

298. 17.beta.-estra-1,3,5(10)-triene-3,17-diol

299. Estradiol [mi]

300. Estradiol [hsdb]

301. Estradiol [inci]

302. 17.beta.-oestra-1,3,5(10)-triene-3,17-diol

303. Opera_id_1688

304. Prestwick0_000441

305. Prestwick1_000441

306. Prestwick2_000441

307. Prestwick3_000441

308. Spectrum5_002055

309. 17beta-estradiol (e2)

310. Estradiol [vandf]

311. 3,17beta-dihydroxy-1,3,5(10)-estratriene

312. Alpha-estradiol (obsolete)

313. Beta-estradiol, >=98%

314. Bmse000642

315. Epitope Id:136018

316. (+)-3,17b-estradiol

317. E 8875

318. Ec 200-023-8

319. Estradiol [usp-rs]

320. Estradiol [who-dd]

321. Schembl8049

322. (+)-3,17beta-estradiol

323. Estradiol (jan/usp/inn)

324. Tritiated Estradiol-17-beta

325. Bidd:pxr0065

326. Lopac0_000503

327. S-21400

328. Bspbio_000482

329. Bspbio_001065

330. Kbiogr_000405

331. Kbiogr_002269

332. Kbioss_000405

333. Kbioss_002270

334. Oestradiol-17beta And Esters

335. Mls000758312

336. Mls001076331

337. Mls001424022

338. Bidd:er0125

339. Oestradiol-17beta And Esters [steroidal Oestrogens]

340. Spbio_002421

341. Estradiol [green Book]

342. Bpbio1_000532

343. Gtpl1012

344. Gtpl1013

345. Estradiol [orange Book]

346. Dtxsid0020573

347. Niosh/kg7030000

348. Bdbm17292

349. Bijuva Component Estradiol

350. Kbio2_000405

351. Kbio2_002269

352. Kbio2_002973

353. Kbio2_004837

354. Kbio2_005541

355. Kbio2_007405

356. Kbio3_000769

357. Kbio3_000770

358. Kbio3_002749

359. Estradiol [usp Monograph]

360. Nsc9895

361. 1a52

362. 1g50

363. 2d06

364. Angeliq Component Estradiol

365. Cmap_000005

366. Estradiol Impurity A [ip]

367. Oriahnn Component Estradiol

368. Prefest Component Estradiol

369. Bio1_000403

370. Bio1_000892

371. Bio1_001381

372. Bio2_000363

373. Bio2_000843

374. Hms1362e07

375. Hms1569i04

376. Hms1792e07

377. Hms1990e07

378. Hms2051c17

379. Hms2090e18

380. Hms2096i04

381. Hms2236h04

382. Hms3261f07

383. Hms3403e07

384. Hms3713i04

385. Hms3884a08

386. Beta-estradiol, Analytical Standard

387. (8s,9s,13s,14s,17s)-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,17-diol

388. Activella Component Estradiol

389. Bcp08579

390. Estradiol 17-beta [vandf]

391. Hy-b0141

392. Estradiol Component Of Bijuva

393. Tox21_111148

394. Tox21_202057

395. Tox21_300288

396. Tox21_500503

397. 1,5-estratriene-3,17.beta.-diol

398. Combipatch Component Estradiol

399. Lmst02010001

400. S1709

401. Zinc13520815

402. Estradiol Component Of Angeliq

403. Estradiol Component Of Oriahnn

404. Estradiol Component Of Prefest

405. Estradiol-17-beta-6,7-(sup 3)h

406. [2,4,6,7-3h]-17beta-estradiol

407. Akos015896570

408. Climara Pro Component Estradiol

409. Ccg-100808

410. Cs-1938

411. Db00783

412. Estradiol Component Of Activella

413. Lp00503

414. Nc00058

415. Sdccgsbi-0050487.p002

416. Estradiol Component Of Combipatch

417. Idi1_002118

418. Smp1_000121

419. Ncgc00091544-00

420. Ncgc00091544-01

421. Ncgc00091544-02

422. Ncgc00091544-05

423. Ncgc00091544-06

424. Ncgc00091544-07

425. Ncgc00091544-09

426. Ncgc00091544-10

427. Ncgc00091544-11

428. Ncgc00091544-12

429. Ncgc00091544-13

430. Ncgc00091544-14

431. Ncgc00091544-15

432. Ncgc00091544-16

433. Ncgc00091544-18

434. Ncgc00091544-27

435. Ncgc00179321-01

436. Ncgc00179321-02

437. Ncgc00254177-01

438. Ncgc00259606-01

439. Ncgc00261188-01

440. 17-e

441. Ac-22346

442. As-13729

443. Cpd000059126

444. Estradiol Component Of Climara Pro

445. Estra-1,3,5(10)-triene-3,17b-diol

446. Oestra-1,3,5(10)-triene-3,17b-diol

447. Wln: L E5 B666ttt&j E1 Fq Oq

448. Estra-1,5(10)-triene-3,17.beta.-diol

449. Estradiol, Meets Usp Testing Specifications

450. 3,17beta-dihydroxyestra-1,3,5(10)-trien

451. Eu-0100503

452. Kg70300000

453. Oestra-1,5(10)-triene-3,17.beta.-diol

454. 17-beta-estradiol 100 Microg/ml In Methanol

455. 17-beta-estradiol 1000 Microg/ml In Methanol

456. C00951

457. D00105

458. (17b)-estra-1,3,5(10)-triene-3,17-diol

459. 13b-methyl-1,3,5(10)-gonatriene-3,17b-ol

460. 17-decahydrocyclopenta[a]phenanthrene-3,17-diol

461. 17.beta.-estra-1,5(10)-triene-3,17-diol

462. 17.beta.-oestra-1,5(10)-triene-3,17-diol

463. Ethinylestradiol Impurity D [ep Impurity]

464. 003e693

465. 17-beta-estradiol 100 Microg/ml In Acetonitrile

466. Q422416

467. Sr-01000721892

468. 13beta-methyl-1,3,5(10)-gonatriene-3,17beta-ol

469. Estra-1,5(10)-triene-3,17-diol (17.beta.)-

470. Estradiol Benzoate Impurity A [ep Impurity]

471. Estradiol Valerate Impurity A [ep Impurity]

472. Q-201503

473. Sr-01000075866-1

474. Sr-01000075866-4

475. Sr-01000721892-3

476. Brd-k18910433-001-04-4

477. Brd-k18910433-001-43-2

478. Estra-1(10),2,4-triene-3,17-diol, (17beta)-

479. Estra-1,5(10)-triene-3,17-diol, (17.beta.)-

480. Z1847670481

481. B8b5aef5-4957-49eb-a14f-444a8212c482

482. Beta-estradiol, Bioreagent, Powder, Suitable For Cell Culture

483. Estradiol, United States Pharmacopeia (usp) Reference Standard

484. 13.beta.-methyl-1,3,5(10)-gonatriene-3,17.beta.-ol

485. Beta-estradiol, Powder, Gamma-irradiated, Suitable For Cell Culture

486. Estra-1,3,5(10)-triene-3,17-diol, (6,7-(sup 3)h,17-beta)-

487. (9beta,13alpha,14beta,17alpha)-estra-1,3,5(10)-triene-3,17-diol

488. Estradiol, Pharmaceutical Secondary Standard; Certified Reference Material

489. (13s,17s)-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6h-cyclopenta[a]phenanthrene-3,17-beta-diol

490. (1s,10r,11s,14s,15s)-15-methyltetracyclo[8.7.0.0;{2,7}.0;{11,15}]heptadeca-2,4,6-triene-5,14-diol

491. 17beta-estradiol Solution, 1.0 Mg/ml In Acetonitrile, Ampule Of 1 Ml, Certified Reference Material

2.4 Create Date

2004-09-16

3 Chemical and Physical Properties

Molecular Formula	C₁₈H₂₄O₂
Molecular Weight	272.4 g/mol
XLogP3	4
Hydrogen Bond Donor Count	2
Hydrogen Bond Acceptor Count	2
Rotatable Bond Count	0
Exact Mass	272.177630004 g/mol
Monoisotopic Mass	272.177630004 g/mol
Topological Polar Surface Area	40.5 Å²
Heavy Atom Count	20
Formal Charge	0
Complexity	382
Isotope Atom Count	0
Defined Atom Stereocenter Count	5
Undefined Atom Stereocenter Count	0
Defined Bond Stereocenter Count	0
Undefined Bond Stereocenter Count	0
Covalently Bonded Unit Count	1

4 Drug and Medication Information

4.1 Therapeutic Uses

Estradiol tablets are indicated in the treatment of moderate to severe vasomotor symptoms associated with the menopause. /Included in US product label/

US Natl Inst Health; DailyMed. Current Medication Information estrace (estradiol) tablet (August 2006). Available from, as of February 22, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=1485

Estradiol tablets are indicated in the treatment of moderate to severe symptoms of vulvar and vaginal atrophy associated with the menopause. When prescribing solely for the treatment of symptoms of vulvar and vaginal atrophy, topical vaginal products should be considered. /Included in US product label/

Estradiol tablets are indicated in the treatment of hypoestrogenism due to hypogonadism, castration or primary ovarian failure. /Included in US product label/

Estradiol tablets are indicated in the treatment of breast cancer (for palliation only) in appropriately selected women and men with metastatic disease. /Included in US product label/

For more Therapeutic Uses (Complete) data for ESTRADIOL (7 total), please visit the HSDB record page.

4.2 Drug Warning

ESTROGENS INCREASE THE RISK OF ENDOMETRIAL CANCER- Close clinical surveillance of all women taking estrogens is important. Adequate diagnostic measures, including endometrial sampling when indicated, should be undertaken to rule out malignancy in all cases of undiagnosed persistent or recurring abnormal vaginal bleeding. There is no evidence that the use of "natural" estrogens results in a different endometrial risk profile than "synthetic" estrogens at equivalent estrogen doses.

CARDIOVASCULAR AND OTHER RISKS- Estrogens with or without progestins should not be used for the prevention of cardiovascular disease.

The Women's Health Initiative (WHI) study reported increased risks of myocardial infarction, stroke, invasive breast cancer, pulmonary emboli, and deep vein thrombosis in postmenopausal women (50 to 79 years of age) during 5 years of treatment with oral conjugated estrogens (CE 0.625 mg) combined with medroxyprogesterone acetate (MPA 2.5 mg) relative to placebo.

The Women's Health Initiative Memory Study (WHIMS), a substudy of WHI, reported increased risk of developing probable dementia in postmenopausal women 65 years of age or older during 4 years of treatment with oral conjugated estrogens plus medroxyprogesterone acetate relative to placebo. It is unknown whether this finding applies to younger postmenopausal women or to women taking estrogen alone therapy.

For more Drug Warnings (Complete) data for ESTRADIOL (48 total), please visit the HSDB record page.

4.3 Drug Indication

Estradiol is indicated in various preparations for the treatment of moderate to severe vasomotor symptoms and vulvar and vaginal atrophy due to menopause, for the treatment of hypoestrogenism due to hypogonadism, castration, or primary ovarian failure, and for the prevention of postmenopausal osteoporosis. It is also used for the treatment of breast cancer (only for palliation therapy) in certain men or women with metastatic disease, and for the treatment of androgen-dependent prostate cancer (only for palliation therapy). It is also used in combination with other hormones as a component of oral contraceptive pills for preventing pregnancy (most commonly as [DB00977], a synthetic form of estradiol). **A note on duration of treatment** Recommendations for treatment of menopausal symptoms changed drastically following the release of results and early termination of the Women's Health Initiative (WHI) studies in 2002 as concerns were raised regarding estrogen use. Specifically, the combined estrogenprogestin group was discontinued after about 5 years of follow up due to a statistically significant increase in invasive breast cancer and in cardiovascular events. Following extensive critique of the WHI results, Hormone Replacement Therapy (HRT) is now recommended to be used only for a short period (for 3-5 years postmenopause) in low doses, and in women without a history of breast cancer or increased risk of cardiovascular or thromboembolic disease. Estrogen for postmenopausal symptoms should always be given with a progestin component due to estrogen's stimulatory effects on the endometrium; in women with an intact uterus, unopposed estrogen has been shown to promote the growth of the endometrium which can lead to endometrial hyperplasia and possibly cancer over the long-term.

FDA Label

5 Pharmacology and Biochemistry

5.1 Pharmacology

Estradiol acts on the on the estrogen receptors to relieve vasomotor systems (such as hot flashes) and urogenital symptoms (such as vaginal dryness and dyspareunia). Estradiol has also been shown to exert favorable effects on bone density by inhibiting bone resorption. Estrogen appears to inhibit bone resorption and may have beneficial effects on the plasma lipid profile. Estrogens cause an increase in hepatic synthesis of various proteins, which include sex hormone binding globulin (SHBG), and thyroid-binding globulin (TBG). Estrogens are known to suppress the formation of follicle-stimulating hormone (FSH) in the anterior pituitary gland. **A note on hyper-coagulable state, cardiovascular health, and blood pressure** Estradiol may cause an increased risk of cardiovascular disease, DVT, and stroke, and its use should be avoided in patients at high risk of these conditions. Estrogen induces a hyper-coagulable state, which is also associated with both estrogen-containing oral contraceptive (OC) use and pregnancy. Although estrogen causes an increase in levels of plasma renin and angiotensin. Estrogen-induced increases in angiotensin, causing sodium retention, which is likely to be the mechanism causing hypertension after oral contraceptive treatment.

5.2 MeSH Pharmacological Classification

Estrogens

Compounds that interact with ESTROGEN RECEPTORS in target tissues to bring about the effects similar to those of ESTRADIOL. Estrogens stimulate the female reproductive organs, and the development of secondary female SEX CHARACTERISTICS. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. (See all compounds classified as Estrogens.)

5.3 FDA Pharmacological Classification

5.3.1 Active Moiety

ESTRADIOL

5.3.2 FDA UNII

4TI98Z838E

5.3.3 Pharmacological Classes

Estrogen Receptor Agonists [MoA]; Estrogen [EPC]; Estradiol Congeners [CS]

5.4 ATC Code

G - Genito urinary system and sex hormones

G03 - Sex hormones and modulators of the genital system

G03C - Estrogens

G03CA - Natural and semisynthetic estrogens, plain

G03CA03 - Estradiol

5.5 Absorption, Distribution and Excretion

Absorption

The absorption of several formulations of estradiol is described below: Oral tablets and injections First-pass metabolism in the gastrointestinal tract rapidly breaks down estradiol tablets before entering the systemic circulation. The bioavailability of oral estrogens is said to be 2-10% due to significant first-pass effects. The esterification of estradiol improves the administration (such as with estradiol valerate) or to sustain release from intramuscular depot injections (including estradiol cypionate) via higher lipophilicity. After absorption, the esters are cleaved, which leads to the release of endogenous estradiol, or 17-estradiol. Transdermal preparations The transdermal preparations slowly release estradiol through intact skin, which sustains circulating levels of estradiol during a 1 week period of time. Notably, the bioavailability of estradiol after transdermal administration is about 20 times higher than after oral administration. Transdermal estradiol avoids first pass metabolism effects that reduce bioavailability. Administration via the buttock leads to a Cmax of about 174 pg/mL compared to 147 pg/mL via the abdomen. Spray preparations After daily administration, the spray formulations of estradiol reach steady state within 7-8 days. After 3 sprays daily, Cmax is about 54 pg/mL with a Tmax of 20 hours. AUC is about 471 pghr/mL. Vaginal ring and cream preparations Estradiol is efficiently absorbed through the mucous membranes of the vagina. The vaginal administration of estrogens evades first-pass metabolism. Tmax after vaginal ring delivery ranges from 0.5 to 1 hour. Cmax is about 63 pg/mL. The vaginal cream preparation has a Cmax of estradiol (a component of Premarin vaginal estrogen conjugate cream) was a Cmax of 12.8 16.6 pg/mL, Tmax of 8.5 6.2 hours, with an AUC of 231 285 pghr/mL.

Route of Elimination

Estradiol is excreted in the urine with both glucuronide and sulfate conjugates.

Volume of Distribution

Estrogens administered exogenously distribute in a similar fashion to endogenous estrogens. They can be found throughout the body, especially in the sex hormone target organs, such as the breast, ovaries and uterus.

Clearance

In one pharmacokinetic study, the clearance of orally administered micronized estradiol in postmenopausal women was 29.915.5 mL/min/kg. Another study revealed a clearance of intravenously administered estradiol was 1.3 mL/min/kg.

Estrogens used in therapeutics are well absorbed through the skin, mucous membranes, and the gastrointestinal (GI) tract. The vaginal delivery of estrogens circumvents first-pass metabolism.

US Natl Inst Health; DailyMed. Current Medication Information ESTRING (estradiol) ring (October 2009). Available from, as of February 22, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=11686

The Estradiol Transdermal System Continuous Delivery (Once-Weekly) continuously releases estradiol which is transported across intact skin leading to sustained circulating levels of estradiol during a 7 day treatment period. The systemic availability of estradiol after transdermal administration is about 20 times higher than that after oral administration. This difference is due to the absence of first-pass metabolism when estradiol is given by the transdermal route.

US Natl Inst Health; DailyMed. Current Medication Information ESTRADIOL patch (September 2009). Available from, as of February 23, 2010: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=12806

In a Phase I study of 14 postmenopausal women, the insertion of ESTRING (estradiol vaginal ring) rapidly increased serum estradiol (E2) levels. The time to attain peak serum estradiol levels (Tmax) was 0.5 to 1 hour. Peak serum estradiol concentrations post-initial burst declined rapidly over the next 24 hours and were virtually indistinguishable from the baseline mean (range: 5 to 22 pg/mL). Serum levels of estradiol and estrone (E1) over the following 12 weeks during which the ring was maintained in the vaginal vault remained relatively unchanged

Table: PHARMACOKINETIC MEAN ESTIMATES FOLLOWING SINGLE ESTRING APPLICATION [Table#4651]

[Table#4651]

The initial estradiol peak post-application of the second ring in the same women resulted in ~38 percent lower Cmax, apparently due to reduced systemic absorption via the treated vaginal epithelium. The relative systemic exposure from the initial peak of ESTRING accounted for approximately 4 percent of the total estradiol exposure over the 12-week period.

For more Absorption, Distribution and Excretion (Complete) data for ESTRADIOL (17 total), please visit the HSDB record page.

5.6 Metabolism/Metabolites

Exogenously administered estrogens are metabolized in the same fashion as endogenous estrogens. Metabolic transformation occurs primarily in the liver and intestine. Estradiol is metabolized to estrone, and both are converted to estriol, which is later excreted in the urine. Sulfate and glucuronide conjugation estrogens also take place in the liver. Biliary secretion of metabolic conjugates are released into the intestine, and estrogen hydrolysis in the gut occurs, followed by reabsorption. The CYP3A4 hepatic cytochrome enzyme is heavily involved in the metabolism of estradiol. CYP1A2 also plays a role.

Exogenous estrogens are metabolized in the same manner as endogenous estrogens. Circulating estrogens exist in a dynamic equilibrium of metabolic interconversions. These transformations take place mainly in the liver. Estradiol is converted reversibly to estrone, and both can be converted to estriol, which is the major urinary metabolite. Estrogens also undergo enterohepatic recirculation via sulfate and glucuronide conjugation in the liver, biliary secretion of conjugates into the intestine, and hydrolysis in the gut followed by reabsorption. In postmenopausal women, a significant proportion of the circulating estrogens exist as sulfate conjugates, especially estrone sulfate, which serves as a circulating reservoir for the formation of more active estrogens.

US Natl Inst Health; DailyMed. Current Medication Information estrace (estradiol) tablet (August 2006).

Variations in estradiol metabolism ... depend upon the stage of the menstrual cycle ... In general, the hormone undergoes rapid hepatic biotransformation with a plasma half-life measured in minutes.

Hardman, J.G., L.E. Limbird, P.B. Molinoff, R.W. Ruddon, A.G. Goodman (eds.). Goodman and Gilman's The Pharmacological Basis of Therapeutics. 9th ed. New York, NY: McGraw-Hill, 1996., p. 1420

Estradiol is primarily converted ... to estriol, which is the major urinary metabolite. A variety of sulfate and glucuronide conjugates also are excreted in the urine.

Hardman, J.G., L.E. Limbird, P.B. Molinoff, R.W. Ruddon, A.G. Goodman (eds.). Goodman and Gilman's The Pharmacological Basis of Therapeutics. 9th ed. New York, NY: McGraw-Hill, 1996., p. 1420

The metabolism of estradiol-17beta and estrone is similar in rats and in humans, in that both species transform these steroids mainly by (aromatic) 2-hydroxylation, and also by 16alpha-hydroxylation. Glucuronides of the various metabolites are excreted in the bile. Differences in the metabolism of estrogens by humans and rats lie mostly in the type of conjugation. A relatively large proportion of administered estrone, estradiol-17beta and estriol is transformed in rats to metabolites oxygenated both at C-2 and C-16. When estriol is administered to rats, glucuronides and, to a lesser extent, sulfates of 16-ketooestradiol and of 2- and 3-methyl ethers of 2-hydroxyoestriol and 2-hydroxy-16-ketooestradiol are excreted in the bile. In contrast, hydroxylations at C-6 or C-7 of ring B of estradiol-17beta and estrone are a minor pathway in rats. 2-Hydroxyoestrogens ('catechol estrogens') are further transformed by various routes, including covalent binding to proteins.

IARC. Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Geneva: World Health Organization, International Agency for Research on Cancer, 1972-PRESENT. (Multivolume work). Available at: https://monographs.iarc.fr/ENG/Classification/index.php, p. V21 307 (1979)

For more Metabolism/Metabolites (Complete) data for ESTRADIOL (8 total), please visit the HSDB record page.

5.7 Biological Half-Life

The terminal half-lives for various estrogen products post oral or intravenous administration has been reported to range from 1-12 hours. One pharmacokinetic study of oral estradiol valerate administration in postmenopausal women revealed a terminal elimination half-life of 16.9 6.0 h. A pharmacokinetic study of intravenous estradiol administration in postmenopausal women showed an elimination half-life of 27.45 5.65 minutes. The half-life of estradiol appears to vary by route of administration.

... After oral administration ... the terminal half life was 20.1 hr ...

5.8 Mechanism of Action

Estrogen is found in the the breast, uterine, ovarian, skin, prostate, bone, fat, and brain tissues. The main source of estrogen in adult women during the reproductive period of life is the ovarian follicle, which secretes 70 to 500 mcg of estradiol each day. After menopause, however, the majority of endogenous estrogen is produced by transformation of androstenedione (which is secreted by the adrenal cortex) to estrone in the peripheral tissues. Both estrone and its sulphate conjugated form, estrone sulphate, represent the most abundant estrogens found in postmenopausal women. Estradiol, however, is considerably more potent than estrone and estriol at the estrogen receptor (ER). As a result, the higher estrone concentration in postmenopausal population, can cause various undesirable effects. These effects may include hot flashes, chills, vaginal dryness, mood swings, irregular menstruation, and chills, in addition to sleep problems. Estradiol workings by binding to subtypes of the estrogen receptor: estrogen receptor alpha (ER) and estrogen receptor beta (ER). It also exerts potent agonism of G Protein-coupled estrogen receptor (GPER), which is recognized an important regulator of this drug's rapid effects. Once the estrogen receptor has bound to its ligand, it enters the nucleus of the target cell, regulating gene transcription and formation of of messenger RNA. This mRNA makes contact with ribosomes producing specific proteins that express the effect of estradiol upon the target cell. Agonism of estrogen receptors increases pro-estrogenic effects, leading to the relief of vasomotor and urogenital symptoms of a postmenopausal or low estradiol state.

Endogenous estrogens are largely responsible for the development and maintenance of the female reproductive system and secondary sexual characteristics. Although circulating estrogens exist in a dynamic equilibrium of metabolic interconversions, estradiol is the principal intracellular human estrogen and is substantially more potent than its metabolites, estrone and estriol at the receptor level. ... After menopause, most endogenous estrogen is produced by conversion of androstenedione, secreted by the adrenal cortex, to estrone by peripheral tissues. Thus, estrone and the sulfate conjugated form, estrone sulfate, are the most abundant circulating estrogens in postmenopausal women. Estrogens act through binding to nuclear receptors in estrogen-responsive tissues. To date, two estrogen receptors have been identified. These vary in proportion from tissue to tissue. Circulating estrogens modulate the pituitary secretion of the gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH), through a negative feedback mechanism. Estrogens act to reduce the elevated levels of these hormones seen in postmenopausal women.

Estrogens have an important role in the reproductive, skeletal, cardiovascular, and central nervous systems in women, and act principally by regulating gene expression. Biologic response is initiated when estrogen binds to a ligand-binding domain of the estrogen receptor resulting in a conformational change that leads to gene transcription through specific estrogen response elements (ERE) of target gene promoters; subsequent activation or repression of the target gene is mediated through 2 distinct transactivation domains (ie, AF-1 and AF-2) of the receptor. The estrogen receptor also mediates gene transcription using different response elements (ie, AP-1) and other signal pathways. Recent advances in the molecular pharmacology of estrogen and estrogen receptors have resulted in the development of selective estrogen receptor modulators (eg, clomiphene, raloxifene, tamoxifen, toremifene), agents that bind and activate the estrogen receptor but that exhibit tissue-specific effects distinct from estrogen. Tissue-specific estrogen-agonist or -antagonist activity of these drugs appears to be related to structural differences in their estrogen receptor complex (eg, specifically the surface topography of AF-2 for raloxifene) compared with the estrogen (estradiol)-estrogen receptor complex. A second estrogen receptor also has been identified, and existence of at least 2 estrogen receptors (ER-alpha, ER-beta) may contribute to the tissue-specific activity of selective modulators. While the role of the estrogen receptor in bone, cardiovascular tissue, and the CNS continues to be studied, emerging evidence indicates that the mechanism of action of estrogen receptors in these tissues differs from the manner in which estrogen receptors function in reproductive tissue. /Estrogen General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2010. Bethesda, MD. (2010), p. 3130

Intracellular cytosol-binding proteins for estrogens have been identified in estrogen-responsive tissues including the female genital organs, breasts, pituitary, and hypothalamus. The estrogen-binding protein complex (ie, cytosol-binding protein and estrogen) distributes into the cell nucleus where it stimulates DNA, RNA, and protein synthesis. The presence of these receptor proteins is responsible for the palliative response to estrogen therapy in women with metastatic carcinoma of the breast. /Estrogen General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2010. Bethesda, MD. (2010), p. 3130

Estrogens have generally favorable effects on blood cholesterol and phospholipid concentrations. Estrogens reduce LDL-cholesterol and increase HDL-cholesterol concentrations in a dose-related manner. The decrease in LDL-cholesterol concentrations associated with estrogen therapy appears to result from increased LDL catabolism, while the increase in triglyceride concentrations is caused by increased production of large, triglyceride-rich, very-low-density lipoproteins (VLDLs); changes in serum HDL-cholesterol concentrations appear to result principally from an increase in the cholesterol and apolipoprotein A-1 content of HDL2- and a slight increase in HDL3-cholesterol. /Estrogen General Statement/

American Society of Health System Pharmacists; AHFS Drug Information 2010. Bethesda, MD. (2010), p. 3130

For more Mechanism of Action (Complete) data for ESTRADIOL (7 total), please visit the HSDB record page.

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