Allopregnanolone

Allopregnanolone
Clinical data
Trade names	Zulresso
Other names	ALLO; ALLOP; SAGE-547; SGE-102; 5α-Pregnan-3α-ol-20-one; 5α-Pregnane-3α-ol-20-one; 3α-Hydroxy-5α-pregnan-20-one; 3α,5α-Tetrahydroprogesterone; 3α,5α-THP, brexanolone (USAN US)
AHFS/Drugs.com	Monograph
MedlinePlus	a619037
License data	US DailyMed: Brexanolone; US FDA: Zulresso;
Routes of; administration	Intravenous
Drug class	Neurosteroids; Antidepressants
ATC code	N06AX29 (WHO) ;
Legal status
Legal status	US: Schedule IV;
Pharmacokinetic data
Bioavailability	Oral: <5%
Protein binding	>99%
Metabolism	Non-CYP450 (keto-reduction via aldo-keto reductases (AKR), glucuronidation via glucuronosyltransferases (UGT), sulfation via sulfotransferases (SULT))
Elimination half-life	9 hours
Excretion	Feces: 47%; Urine: 42%
Identifiers
	IUPAC name 1-[(3R,5S,8R,9S,10S,13S,14S,17S)-3-hydroxy-10,13-dimethyl-2,3,4,5,6,7,8,9,11,12,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-17-yl]ethanone;
CAS Number	516-54-1;
PubChem CID	92786;
DrugBank	DB11859;
ChemSpider	83760;
UNII	S39XZ5QV8Y;
KEGG	D11149;
ChEBI	CHEBI:50169;
ChEMBL	ChEMBL207538;
CompTox Dashboard (EPA)	DTXSID901016239 DTXSID1046342, DTXSID901016239 ;
Chemical and physical data
Formula	C21H34O2
Molar mass	318.501 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES CC(=O)[C@H]1CC[C@@H]2[C@@]1(CC[C@H]3[C@H]2CC[C@@H]4[C@@]3(CC[C@H](C4)O)C)C;
	InChI InChI=1S/C21H34O2/c1-13(22)17-6-7-18-16-5-4-14-12-15(23)8-10-20(14,2)19(16)9-11-21(17,18)3/h14-19,23H,4-12H2,1-3H3/t14-,15+,16-,17+,18-,19-,20-,21+/m0/s1; Key:AURFZBICLPNKBZ-SYBPFIFISA-N;

Allopregnanolone is a naturally occurring neurosteroid which is made in the body from the hormone progesterone. As a medication, allopregnanolone was referred to as brexanolone, sold under the brand name Zulresso, and was used to treat postpartum depression. It was given by injection into a vein.

Side effects of brexanolone may include sedation, sleepiness, dry mouth, hot flashes, and loss of consciousness. It was a neurosteroid and acts as a positive allosteric modulator of the GABA_A receptor, the major biological target of the inhibitory neurotransmitter γ-aminobutyric acid (GABA).

Brexanolone was approved for medical use in the United States in 2019 and withdrawn from approval in 2025. The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication. The long administration time, as well as the cost for a one-time treatment, have raised concerns about accessibility for many women.