PeptideCompareAllopregnanolone — EU research guide.
Allopregnanolone is a naturally occurring neurosteroid that modulates GABA-A receptors; the same molecule, brexanolone, was developed as an intravenous drug for postpartum depression. A vendor research vial is not the licensed product.
What is Allopregnanolone?
Allopregnanolone (3α-hydroxy-5α-pregnan-20-one) is a naturally occurring C21 pregnane neurosteroid. Neurosteroids of this kind are positive allosteric modulators of GABA-A receptors and enhance receptor function through non-genomic mechanisms, which gives sedative, anxiolytic, anticonvulsant and anaesthetic-type effects. Brexanolone is the same molecule, developed as an intravenous drug for postpartum depression and sold as Zulresso; zuranolone is a related oral synthetic neuroactive steroid.
What does the research show?
A phase 2 trial in 21 women with severe postpartum depression found a HAM-D reduction of 21.0 points at 60 hours with brexanolone versus 8.8 with placebo (difference -12.2, 95% CI -20.77 to -3.67, p=0.0075) (Kanes 2017). Two phase 3 trials followed at 30 US sites (Meltzer-Brody 2018). In study 1 (severe PPD, 138 randomised) the HAM-D change at hour 60 was -19.5 and -17.7 in the two brexanolone arms versus -14.0 with placebo (differences -5.5, 95% CI -8.8 to -2.2, and -3.7, 95% CI -6.9 to -0.5). In study 2 (moderate PPD, 108 randomised) the change was -14.6 with brexanolone versus -12.1 with placebo (difference -2.5, 95% CI -4.5 to -0.5), a smaller effect. Group sizes differ between sources: the Lancet paper reports 138 and 108 randomised, whereas the FDA efficacy analysis used 122 and 104. These trials led to US approval in 2019 for postpartum depression in patients aged 15 and over, given as a 60-hour hospital infusion under a REMS programme. Human evidence is limited to this intravenous formulation and indication, with small samples and short follow-up; no human trial data exist for unformulated research vials.
EU legal status
Brexanolone (Zulresso) was approved by the US FDA in 2019, but no EU marketing authorisation for brexanolone or allopregnanolone was found. Sage discontinued Zulresso at the end of 2024 as a commercial decision, and the US approval was withdrawn at the company's request effective 14 April 2025 (not a safety or effectiveness finding). In the EU, the related oral neurosteroid zuranolone (Zurzuvae capsules, holder Biogen Netherlands B.V.) was authorised on 17 September 2025 for postpartum depression in adults; the EMA overview reports depression scores falling by about 16 points versus about 12 with placebo by day 15. A vendor research vial of allopregnanolone is not an authorised medicine anywhere as far as this research found. Allopregnanolone is not named on the 2026 WADA Prohibited List (as read from a national anti-doping agency copy), but whether category S0 (non-approved substances) applies could not be resolved.
Molecular information
Pharmacokinetics
Potency retained over time
Each line is one storage condition: it starts at 100% and falls as potency is lost. Above the dashed 80% line the material is considered reliable — hover for exact values.
⚠ A structural estimate, derived from each compound's sequence length, cyclisation and oxidation-, deamidation- and light-sensitive residues. Indicative only — not lab-measured per batch.
Allopregnanolone across EU suppliers
COA-verified EU vendors · Updated monthly
References
- Phase 2 randomised trial (n=21): HAM-D reduction of 21.0 versus 8.8 points at 60 hours in severe postpartum depression. Kanes S, Colquhoun H, Gunduz-Bruce H, et al. Lancet 2017;390(10093):480-489. DOI
- Two phase 3 trials (n=138 and n=108): HAM-D differences versus placebo at hour 60, smaller in moderate postpartum depression. Meltzer-Brody S, Colquhoun H, Riesenberg R, et al. Lancet 2018;392(10152):1058-1070. DOI
- US prescribing information: indication, boxed warning, REMS, Schedule IV status, terminal half-life of about 9 hours, adverse reactions and storage. ZULRESSO (brexanolone) injection, prescribing information. US FDA, revised 2022. Source
- US rule placing brexanolone in Schedule IV, with the abuse-potential basis (sedative effects like benzodiazepines). Drug Enforcement Administration. Schedules of Controlled Substances: Placement of Brexanolone in Schedule IV. Federal Register 2019 (84 FR 27938). Source
- Notice that the US approval of Zulresso was withdrawn on 14 April 2025 at the company's request and that the product is no longer marketed. Food and Drug Administration. Sage Therapeutics, Inc.; Withdrawal of Approval of a New Drug Application for ZULRESSO (brexanolone). Federal Register, 14 March 2025. Source
- EU authorisation on 17 September 2025 of the related oral neurosteroid zuranolone for postpartum depression. European Medicines Agency. Zurzuvae (zuranolone): EPAR and medicine overview. Source