17α-estradiol

Alfatradiol

Clinical data
AHFS/Drugs.com	International Drug Names
Pregnancy category	US: C (Risk not ruled out) No studies
Routes of administration	Topical
ATC code	none
Legal status
Legal status	US: ℞-only
Identifiers
IUPAC name Estra-1,3,5(10)-triene-3,17α-diol
Synonyms	17-Epiestradiol
CAS Number	57-91-0 Y
PubChem CID	68570
ChemSpider	61840 Y
UNII	3VQ38D63M7
ChEBI	CHEBI:17160 Y
ChEMBL	CHEMBL286452 Y
ECHA InfoCard	100.000.322
Chemical and physical data
Formula	C18H24O2
Molar mass	272.37 g/mol
3D model (Jmol)	Interactive image
SMILES OC1CCC3C1(C)CCC(c2cc4)C3CCc2cc4O
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 Y Key:VOXZDWNPVJITMN-SFFUCWETSA-N Y

Alfatradiol (INN) (brand names Ell-Cranell Alpha, Pantostin in Germany), also known as 17α-estradiol or as 17-epiestradiol, is a steroidal weak estrogen and potent 5α-reductase inhibitor used topically in the treatment of androgenic alopecia (hair loss) in men and women. It is a stereoisomer of the endogenous steroid hormone 17β-estradiol.

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. 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.

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. 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.

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.