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Not to be confused with 17β-estradiol.
Alfatradiol skeletal.svg
Systematic (IUPAC) name
Clinical data
AHFS/ International Drug Names
Pregnancy cat. C (US) No studies
Legal status -only (US) Pharmacy only
Routes Topical
CAS number 57-91-0 YesY
ATC code None
PubChem CID 68570
ChemSpider 61840 YesY
UNII 3VQ38D63M7 YesY
ChEBI CHEBI:17160 YesY
Synonyms 17-Epiestradiol
Chemical data
Formula C18H24O2 
Mol. mass 272.37 g/mol
 YesY (what is this?)  (verify)

Alfatradiol (INN,[1] or 17α-estradiol, trade names Ell-Cranell Alpha and Pantostin in Germany) is a 5α-reductase inhibitor used topically for the treatment of androgenic alopecia (hair loss) in men and women.[2]


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.[3] 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 is thought to be a consequence of the hair roots being lost.[4]

A study (founded by 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.[5]


Nothing is known about the use of alfatradiol during pregnancy or lactation, or in patients under 18 years of age. It should not be used under these circumstances.[6]

Adverse effects[edit]

Local burning or itching is not an effect of alfatradiol, but of the ethanol in the solvent. The solution can stimulate sebum production.[6]

Chemistry and pharmacology[edit]

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. Contrary to estradiol, alfatradiol has no estrogen activity, but instead acts as an inhibitor of the enzyme 5α-reductase which is responsible for the activation of testosterone to dihydrotestosterone, which plays a role in regulating hair growth.[3]

See also[edit]


  1. ^ "Recommended International Nonproprietary Names (rec. Inn): List 46". WHO Drug Information 15 (3&4). 2001. 
  2. ^ Berger, Artur; Wachter, Helmut, eds. (1998). Hunnius Pharmazeutisches Wörterbuch (in German) (8 ed.). Walter de Gruyter Verlag. p. 486. ISBN 3-11-015793-4. 
  3. ^ a b Mutschler, Ernst; Gerd Geisslinger; Heyo K. Kroemer; Monika Schäfer-Korting (2001). Arzneimittelwirkungen (in German) (8 ed.). Stuttgart: Wissenschaftliche Verlagsgesellschaft. p. 453. ISBN 3-8047-1763-2. 
  4. ^ Jasek, W, ed. (2007). Austria-Codex (in German) 4 (2007/2008 ed.). Vienna: Österreichischer Apothekerverlag. p. 9673. ISBN 978-3-85200-181-4. 
  5. ^ Blume-Peytavi, U.; Kunte, C.; Krisp, A.; Bartels, N. G.; Ellwanger, U.; Hoffmann, R. (2007). "Comparison of the efficacy and safety of topical minoxidil and topical alfatradiol in the treatment of androgenetic alopecia in women". JDDG 5 (5): 391. doi:10.1111/j.1610-0387.2007.06295.x. PMID 17451383.  edit
  6. ^ a b Dootz, Hildegard (ed.). Rote Liste (in German) (2005 ed.). Aulendorf: Editio Cantor Verlag. 32 369. ISBN 3-87193-306-6.