Alfatradiol

Alfatradiol, also known as 17α-estradiol and sold under the brand names Avicis, Avixis, Ell-Cranell Alpha, and Pantostin, is a weak estrogen and 5α-reductase inhibitor medication which is used topically in the treatment of pattern hair loss (androgenic alopecia or pattern baldness) in men and women.[1][2][3][4] It is a stereoisomer of the endogenous steroid hormone and estrogen 17β-estradiol (or simply estradiol).[1]

This article is about 17α-estradiol as a medication. For its role as a hormone, see 17α-Estradiol.

Alfatradiol
Clinical data
Trade namesAvicis, Avixis, Ell-Cranell Alpha, Pantostin
Other names17α-Estradiol; 17-Epiestradiol; MX-4509; Estra-1,3,5(10)-triene-3,17α-diol; β-Estradiol (obsolete, misleading)[1]
AHFS/Drugs.comInternational Drug Names
Pregnancy
category
  • No studies
Routes of
administration		Topical
Drug classEstrogen; 5α-Reductase inhibitor
ATC code
  • None
Legal status
Legal status
Identifiers
CAS Number
PubChem CID
ChemSpider
UNII
ChEBI
ChEMBL
Chemical and physical data
FormulaC18H24O2
Molar mass272.388 g·mol−1
3D model (JSmol)
  (verify)

Medical uses

Alfatradiol is used in form of an ethanolic solution for topical application on the scalp. Similarly to other drugs against alopecia, topical or oral, it has to be applied continuously to prevent further hair loss.[5] Regrowth of hair that was already lost is only possible to a limited extent. In general, advanced alopecia does not respond well to medical treatment, which has historically been thought to be a consequence of the hair roots being lost.[6]

A university-led study (including several authors who are advisors to companies such as Pfizer) in 103 women comparing alfatradiol to minoxidil, another topical hair loss treatment, found the latter to be more effective. In contrast to minoxidil, alfatradiol did not result in an increase of hair density or thickness, but only in slowing down or stabilization of hair loss in this study.[7] In an earlier study, no systemic side effects were noted, and 17α-estradiol was found to reduce androgenic hair loss, though it was not effective at growing new hair.[8]

Other efforts of alfatradiol had been directed at neurodegenerative diseases including Parkinson's.[9]

Other hair loss medications include ketoconazole, finasteride, and dutasteride.

Contraindications

Nothing is known about the use of alfatradiol during pregnancy or lactation, or in patients under 18 years of age. The package leaflet recommends against using it under these circumstances.[10]

Side effects

Local burning or itching is not an effect of alfatradiol, but of the ethanol in the solvent. The solution can stimulate sebum production.[10]

Pharmacology

Pharmacodynamics
Alfatradiol (top) and 17β-estradiol (bottom).

Alfatradiol (17α-estradiol) is distinguished from estradiol (17β-estradiol), the predominant sex hormone in females, only by the stereochemistry of the carbon atom 17. In contrast to 17β-estradiol, 17α-estradiol, while it still binds to the estrogen receptor, has less or no feminizing estrogenic activity depending on its dosage and the tissue it is affecting.[11] Alfatradiol acts as an inhibitor of the enzyme 5α-reductase, which is responsible for the activation of testosterone to dihydrotestosterone, and which plays a role in regulating hair growth.[5] 17α-Estradiol has been studied as a therapeutic with potential to treat Alzheimer's and Parkinson's disease and other patients suffering from neurodegenerative diseases.[12] 17α-Estradiol (as the sodium salt of its sulfated form) is a minor component (<10%) of hormone replacement products (such as conjugated estrogens, brand name Premarin), which have been studied and/or marketed in women and men since the 1930s. A survey of the effects of various forms of 17α-estradiol in humans on biochemical parameters, efficacy, estrogenicity, metabolism, safety, and tolerability has been published.[13]

Alfatradiol binds to the ERα and ERβ with 58% and 11% of the relative binding affinity of 17β-estradiol.[14] However, it has 100-fold lower estrogenic activity relative to estradiol,[15] which may in part be due to differences in the intrinsic activity of the two compounds. On the other hand, alfatradiol has been found to bind to and activate the brain-expressed ER-X with a greater potency than estradiol, indicating that it may be the predominant endogenous ligand for the receptor.[16] In contrast to estradiol, alfatradiol is not a ligand of the G protein-coupled estrogen receptor (affinity >10 μM).[17]

Affinities of estrogen receptor ligands for the ERα and ERβ
LigandOther namesRelative binding affinities (RBA, %)aAbsolute binding affinities (Ki, nM)aAction
ERαERβERαERβ
EstradiolE2; 17β-Estradiol1001000.115 (0.04–0.24)0.15 (0.10–2.08)Estrogen
EstroneE1; 17-Ketoestradiol16.39 (0.7–60)6.5 (1.36–52)0.445 (0.3–1.01)1.75 (0.35–9.24)Estrogen
EstriolE3; 16α-OH-17β-E212.65 (4.03–56)26 (14.0–44.6)0.45 (0.35–1.4)0.7 (0.63–0.7)Estrogen
EstetrolE4; 15α,16α-Di-OH-17β-E24.03.04.919Estrogen
Alfatradiol17α-Estradiol20.5 (7–80.1)8.195 (2–42)0.2–0.520.43–1.2Metabolite
16-Epiestriol16β-Hydroxy-17β-estradiol7.795 (4.94–63)50??Metabolite
17-Epiestriol16α-Hydroxy-17α-estradiol55.45 (29–103)79–80??Metabolite
16,17-Epiestriol16β-Hydroxy-17α-estradiol1.013??Metabolite
2-Hydroxyestradiol2-OH-E222 (7–81)11–352.51.3Metabolite
2-Methoxyestradiol2-MeO-E20.0027–2.01.0??Metabolite
4-Hydroxyestradiol4-OH-E213 (8–70)7–561.01.9Metabolite
4-Methoxyestradiol4-MeO-E22.01.0??Metabolite
2-Hydroxyestrone2-OH-E12.0–4.00.2–0.4??Metabolite
2-Methoxyestrone2-MeO-E1<0.001–<1<1??Metabolite
4-Hydroxyestrone4-OH-E11.0–2.01.0??Metabolite
4-Methoxyestrone4-MeO-E1<1<1??Metabolite
16α-Hydroxyestrone16α-OH-E1; 17-Ketoestriol2.0–6.535??Metabolite
2-Hydroxyestriol2-OH-E32.01.0??Metabolite
4-Methoxyestriol4-MeO-E31.01.0??Metabolite
Estradiol sulfateE2S; Estradiol 3-sulfate<1<1??Metabolite
Estradiol disulfateEstradiol 3,17β-disulfate0.0004???Metabolite
Estradiol 3-glucuronideE2-3G0.0079???Metabolite
Estradiol 17β-glucuronideE2-17G0.0015???Metabolite
Estradiol 3-gluc. 17β-sulfateE2-3G-17S0.0001???Metabolite
Estrone sulfateE1S; Estrone 3-sulfate<1<1>10>10Metabolite
Estradiol benzoateEB; Estradiol 3-benzoate10???Estrogen
Estradiol 17β-benzoateE2-17B11.332.6??Estrogen
Estrone methyl etherEstrone 3-methyl ether0.145???Estrogen
ent-Estradiol1-Estradiol1.31–12.349.44–80.07??Estrogen
Equilin7-Dehydroestrone13 (4.0–28.9)13.0–490.790.36Estrogen
Equilenin6,8-Didehydroestrone2.0–157.0–200.640.62Estrogen
17β-Dihydroequilin7-Dehydro-17β-estradiol7.9–1137.9–1080.090.17Estrogen
17α-Dihydroequilin7-Dehydro-17α-estradiol18.6 (18–41)14–320.240.57Estrogen
17β-Dihydroequilenin6,8-Didehydro-17β-estradiol35–6890–1000.150.20Estrogen
17α-Dihydroequilenin6,8-Didehydro-17α-estradiol20490.500.37Estrogen
Δ8-Estradiol8,9-Dehydro-17β-estradiol68720.150.25Estrogen
Δ8-Estrone8,9-Dehydroestrone19320.520.57Estrogen
EthinylestradiolEE; 17α-Ethynyl-17β-E2120.9 (68.8–480)44.4 (2.0–144)0.02–0.050.29–0.81Estrogen
MestranolEE 3-methyl ether?2.5??Estrogen
MoxestrolRU-2858; 11β-Methoxy-EE35–435–200.52.6Estrogen
Methylestradiol17α-Methyl-17β-estradiol7044??Estrogen
DiethylstilbestrolDES; Stilbestrol129.5 (89.1–468)219.63 (61.2–295)0.040.05Estrogen
HexestrolDihydrodiethylstilbestrol153.6 (31–302)60–2340.060.06Estrogen
DienestrolDehydrostilbestrol37 (20.4–223)56–4040.050.03Estrogen
Benzestrol (B2)–114???Estrogen
ChlorotrianiseneTACE1.74?15.30?Estrogen
TriphenylethyleneTPE0.074???Estrogen
TriphenylbromoethyleneTPBE2.69???Estrogen
TamoxifenICI-46,4743 (0.1–47)3.33 (0.28–6)3.4–9.692.5SERM
Afimoxifene4-Hydroxytamoxifen; 4-OHT100.1 (1.7–257)10 (0.98–339)2.3 (0.1–3.61)0.04–4.8SERM
Toremifene4-Chlorotamoxifen; 4-CT??7.14–20.315.4SERM
ClomifeneMRL-4125 (19.2–37.2)120.91.2SERM
CyclofenilF-6066; Sexovid151–152243??SERM
NafoxidineU-11,000A30.9–44160.30.8SERM
Raloxifene–41.2 (7.8–69)5.34 (0.54–16)0.188–0.5220.2SERM
ArzoxifeneLY-353,381??0.179?SERM
LasofoxifeneCP-336,15610.2–16619.00.229?SERM
OrmeloxifeneCentchroman??0.313?SERM
Levormeloxifene6720-CDRI; NNC-460,0201.551.88??SERM
OspemifeneDeaminohydroxytoremifene0.82–2.630.59–1.22??SERM
Bazedoxifene–??0.053?SERM
EtacstilGW-56384.3011.5??SERM
ICI-164,384–63.5 (3.70–97.7)1660.20.08Antiestrogen
FulvestrantICI-182,78043.5 (9.4–325)21.65 (2.05–40.5)0.421.3Antiestrogen
PropylpyrazoletriolPPT49 (10.0–89.1)0.120.4092.8ERα agonist
16α-LE216α-Lactone-17β-estradiol14.6–570.0890.27131ERα agonist
16α-Iodo-E216α-Iodo-17β-estradiol30.22.30??ERα agonist
MethylpiperidinopyrazoleMPP110.05??ERα antagonist
DiarylpropionitrileDPN0.12–0.256.6–1832.41.7ERβ agonist
8β-VE28β-Vinyl-17β-estradiol0.3522.0–8312.90.50ERβ agonist
PrinaberelERB-041; WAY-202,0410.2767–72??ERβ agonist
ERB-196WAY-202,196?180??ERβ agonist
ErteberelSERBA-1; LY-500,307??2.680.19ERβ agonist
SERBA-2–??14.51.54ERβ agonist
Coumestrol–9.225 (0.0117–94)64.125 (0.41–185)0.14–80.00.07–27.0Xenoestrogen
Genistein–0.445 (0.0012–16)33.42 (0.86–87)2.6–1260.3–12.8Xenoestrogen
Equol–0.2–0.2870.85 (0.10–2.85)??Xenoestrogen
Daidzein–0.07 (0.0018–9.3)0.7865 (0.04–17.1)2.085.3Xenoestrogen
Biochanin A–0.04 (0.022–0.15)0.6225 (0.010–1.2)1748.9Xenoestrogen
Kaempferol–0.07 (0.029–0.10)2.2 (0.002–3.00)??Xenoestrogen
Naringenin–0.0054 (<0.001–0.01)0.15 (0.11–0.33)??Xenoestrogen
8-Prenylnaringenin8-PN4.4???Xenoestrogen
Quercetin–<0.001–0.010.002–0.040??Xenoestrogen
Ipriflavone–<0.01<0.01??Xenoestrogen
Miroestrol–0.39???Xenoestrogen
Deoxymiroestrol–2.0???Xenoestrogen
β-Sitosterol–<0.001–0.0875<0.001–0.016??Xenoestrogen
Resveratrol–<0.001–0.0032???Xenoestrogen
α-Zearalenol–48 (13–52.5)???Xenoestrogen
β-Zearalenol–0.6 (0.032–13)???Xenoestrogen
Zeranolα-Zearalanol48–111???Xenoestrogen
Taleranolβ-Zearalanol16 (13–17.8)140.80.9Xenoestrogen
ZearalenoneZEN7.68 (2.04–28)9.45 (2.43–31.5)??Xenoestrogen
ZearalanoneZAN0.51???Xenoestrogen
Bisphenol ABPA0.0315 (0.008–1.0)0.135 (0.002–4.23)19535Xenoestrogen
EndosulfanEDS<0.001–<0.01<0.01??Xenoestrogen
KeponeChlordecone0.0069–0.2???Xenoestrogen
o,p'-DDT–0.0073–0.4???Xenoestrogen
p,p'-DDT–0.03???Xenoestrogen
Methoxychlorp,p'-Dimethoxy-DDT0.01 (<0.001–0.02)0.01–0.13??Xenoestrogen
HPTEHydroxychlor; p,p'-OH-DDT1.2–1.7???Xenoestrogen
TestosteroneT; 4-Androstenolone<0.0001–<0.01<0.002–0.040>5000>5000Androgen
DihydrotestosteroneDHT; 5α-Androstanolone0.01 (<0.001–0.05)0.0059–0.17221–>500073–1688Androgen
Nandrolone19-Nortestosterone; 19-NT0.010.2376553Androgen
DehydroepiandrosteroneDHEA; Prasterone0.038 (<0.001–0.04)0.019–0.07245–1053163–515Androgen
5-AndrostenediolA5; Androstenediol6173.60.9Androgen
4-Androstenediol–0.50.62319Androgen
4-AndrostenedioneA4; Androstenedione<0.01<0.01>10000>10000Androgen
3α-Androstanediol3α-Adiol0.070.326048Androgen
3β-Androstanediol3β-Adiol3762Androgen
Androstanedione5α-Androstanedione<0.01<0.01>10000>10000Androgen
Etiocholanedione5β-Androstanedione<0.01<0.01>10000>10000Androgen
Methyltestosterone17α-Methyltestosterone<0.0001???Androgen
Ethinyl-3α-androstanediol17α-Ethynyl-3α-adiol4.0<0.07??Estrogen
Ethinyl-3β-androstanediol17α-Ethynyl-3β-adiol505.6??Estrogen
ProgesteroneP4; 4-Pregnenedione<0.001–0.6<0.001–0.010??Progestogen
NorethisteroneNET; 17α-Ethynyl-19-NT0.085 (0.0015–<0.1)0.1 (0.01–0.3)1521084Progestogen
Norethynodrel5(10)-Norethisterone0.5 (0.3–0.7)<0.1–0.221453Progestogen
Tibolone7α-Methylnorethynodrel0.5 (0.45–2.0)0.2–0.076??Progestogen
Δ4-Tibolone7α-Methylnorethisterone0.069–<0.10.027–<0.1??Progestogen
3α-Hydroxytibolone–2.5 (1.06–5.0)0.6–0.8??Progestogen
3β-Hydroxytibolone–1.6 (0.75–1.9)0.070–0.1??Progestogen
Footnotes: a = (1) Binding affinity values are of the format "median (range)" (# (#–#)), "range" (#–#), or "value" (#) depending on the values available. The full sets of values within the ranges can be found in the Wiki code. (2) Binding affinities were determined via displacement studies in a variety of in-vitro systems with labeled estradiol and human ERα and ERβ proteins (except the ERβ values from Kuiper et al. (1997), which are rat ERβ). Sources: See template page.
Selected biological properties of endogenous estrogens in rats
EstrogenER RBA (%)Uterine weight (%)UterotrophyLH levels (%)SHBG RBA (%)
Control–100–100–
Estradiol100506 ± 20+++12–19100
Estrone11 ± 8490 ± 22+++?20
Estriol10 ± 4468 ± 30+++8–183
Estetrol0.5 ± 0.2?Inactive?1
17α-Estradiol4.2 ± 0.8????
2-Hydroxyestradiol24 ± 7285 ± 8+b31–6128
2-Methoxyestradiol0.05 ± 0.04101Inactive?130
4-Hydroxyestradiol45 ± 12????
4-Methoxyestradiol1.3 ± 0.2260++?9
4-Fluoroestradiola180 ± 43?+++??
2-Hydroxyestrone1.9 ± 0.8130 ± 9Inactive110–1428
2-Methoxyestrone0.01 ± 0.00103 ± 7Inactive95–100120
4-Hydroxyestrone11 ± 4351++21–5035
4-Methoxyestrone0.13 ± 0.04338++65–9212
16α-Hydroxyestrone2.8 ± 1.0552 ± 42+++7–24<0.5
2-Hydroxyestriol0.9 ± 0.3302+b??
2-Methoxyestriol0.01 ± 0.00?Inactive?4
Notes: Values are mean ± SD or range. ER RBA = Relative binding affinity to estrogen receptors of rat uterine cytosol. Uterine weight = Percentage change in uterine wet weight of ovariectomized rats after 72 hours with continuous administration of 1 μg/hour via subcutaneously implanted osmotic pumps. LH levels = Luteinizing hormone levels relative to baseline of ovariectomized rats after 24 to 72 hours of continuous administration via subcutaneous implant. Footnotes: a = Synthetic (i.e., not endogenous). b = Atypical uterotrophic effect which plateaus within 48 hours (estradiol's uterotrophy continues linearly up to 72 hours). Sources: See template.

Society and culture

Generic names

Alfatradiol is the generic name of the drug and its INN.[2] It is also known as 17α-estradiol.[1]

Brand names

Alfatradiol is marketed under the brand names Avicis, Avixis, Ell-Cranell Alpha, and Pantostin.[2]

Availability

Alfatradiol is available in Germany and several Latin American countries, including Argentina, Brazil, and Mexico.

Research

Alfatradiol administered systemically improved metabolic function, reduced insulin resistance, decreased intra-abdominal fat, and decreased inflammation in old male mice without inducing feminization, suggesting potential usefulness in the treatment of type 2 diabetes.[18]

See also

References
  1. J. Elks (14 November 2014). The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies. Springer. pp. 897–. ISBN 978-1-4757-2085-3.
  2. "Alfatradiol". Drugs.com International.
  3. Berger A, Wachter H, eds. (1998). Hunnius Pharmazeutisches Wörterbuch (in German) (8 ed.). Walter de Gruyter Verlag. p. 486. ISBN 978-3-11-015793-2.
  4. "Recommended International Nonproprietary Names (rec. Inn): List 46". WHO Drug Information. 15 (3&4). 2001.
  5. Mutschler E, Geisslinger G, Kroemer HK, Schäfer-Korting M (2001). Arzneimittelwirkungen (in German) (8 ed.). Stuttgart: Wissenschaftliche Verlagsgesellschaft. p. 453. ISBN 978-3-8047-1763-3.
  6. Jasek W, ed. (2007). Austria-Codex (in German). 4 (2007/2008 ed.). Vienna: Österreichischer Apothekerverlag. p. 9673. ISBN 978-3-85200-181-4.
  7. Blume-Peytavi U, Kunte C, Krisp A, Garcia Bartels N, Ellwanger U, Hoffmann R (May 2007). "Comparison of the efficacy and safety of topical minoxidil and topical alfatradiol in the treatment of androgenetic alopecia in women". Journal der Deutschen Dermatologischen Gesellschaft. 5 (5): 391–5. doi:10.1111/j.1610-0387.2007.06295.x. PMID 17451383.
  8. Orfanos CE, Vogels L (1980). "[Local therapy of androgenetic alopecia with 17 alpha-estradiol. A controlled, randomized double-blind study (author's transl)]". Dermatologica (in German). 161 (2): 124–32. doi:10.1159/000250344. PMID 7398983.
  9. "Alfatradiol". Adis Insight.
  10. Dootz H, ed. (2005). Rote Liste (in German) (2005 ed.). Aulendorf: Editio Cantor Verlag. 32 369. ISBN 978-3-87193-306-6.
  11. Moos WH, Dykens JA, Howell N (2008). "17α-Estradiol: A Less-Feminizing Estrogen". Drug Development Research. 69 (4): 177–184. doi:10.1002/ddr.20244.
  12. Dykens JA, Moos WH, Howell N (June 2005). "Development of 17alpha-estradiol as a neuroprotective therapeutic agent: rationale and results from a phase I clinical study". Annals of the New York Academy of Sciences. 1052: 116–35. doi:10.1196/annals.1347.008. PMID 16024755.
  13. Moos WH, Dykens JA, Nohynek D, Rubinchik E, Howell N (2009). "Review of the Effects of 17α-Estradiol in Humans: A Less Feminizing Estrogen with Neuroprotective Potential". Drug Development Research. 70: 1–21. doi:10.1002/ddr.20284.
  14. Kuiper GG, Carlsson B, Grandien K, Enmark E, Häggblad J, Nilsson S, Gustafsson JA (March 1997). "Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors alpha and beta". Endocrinology. 138 (3): 863–70. doi:10.1210/endo.138.3.4979. PMID 9048584.
  15. Trüeb RM, Lee W (13 February 2014). Male Alopecia: Guide to Successful Management. Springer Science & Business Media. pp. 93–. ISBN 978-3-319-03233-7.
  16. Toran-Allerand CD, Tinnikov AA, Singh RJ, Nethrapalli IS (September 2005). "17alpha-estradiol: a brain-active estrogen?". Endocrinology. 146 (9): 3843–50. doi:10.1210/en.2004-1616. PMID 15947006.
  17. Prossnitz ER, Arterburn JB (July 2015). "International Union of Basic and Clinical Pharmacology. XCVII. G Protein-Coupled Estrogen Receptor and Its Pharmacologic Modulators". Pharmacol. Rev. 67 (3): 505–40. doi:10.1124/pr.114.009712. PMC 4485017. PMID 26023144.
  18. Stout MB, Steyn FJ, Jurczak MJ, Camporez JG, Zhu Y, Hawse JR, et al. (January 2017). "17α-Estradiol Alleviates Age-related Metabolic and Inflammatory Dysfunction in Male Mice Without Inducing Feminization". The Journals of Gerontology. Series A, Biological Sciences and Medical Sciences. 72 (1): 3–15. doi:10.1093/gerona/glv309. PMC 5155656. PMID 26809497.
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