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Allopregnanolone

Neurosteroids
BrexanoloneZulresso3α,5α-THP

Overview

Allopregnanolone, also known as Brexanolone or Zulresso, is an endogenous neurosteroid produced primarily in the central nervous system and peripheral tissues. It belongs to the class of neuroactive steroids, specifically the 3α,5α-tetrahydroprogesterone (3α,5α-THP) derivatives. Allopregnanolone is synthesized from progesterone and is known for its potent modulatory effects on the brain. Researchers have extensively studied its role in modulating mood and stress responses, as well as its potential therapeutic applications in neuropsychiatric disorders. Allopregnanolone plays a crucial role in the modulation of GABAergic neurotransmission, which is pivotal in maintaining the balance of excitatory and inhibitory signals in the brain. Researchers have observed its involvement in mood regulation, stress response, and neuroprotection. It has been a focus of research in conditions such as postpartum depression, anxiety disorders, and epilepsy. The mechanism of action of allopregnanolone involves its interaction with the GABA-A receptor, where it acts as a positive allosteric modulator. This interaction enhances the inhibitory effects of GABA, leading to increased neuronal inhibition and a calming effect on the brain. This mechanism is thought to underlie its therapeutic effects in mood disorders. Pharmacokinetically, allopregnanolone has a relatively short half-life, with rapid metabolism primarily in the liver. Its bioavailability varies by route, with intravenous administration being the most direct. Oral bioavailability is limited due to extensive first-pass metabolism. Clinically, allopregnanolone is approved for use in the treatment of postpartum depression under the trade name Zulresso. It is administered intravenously and has been approved by the FDA in the United States. Its regulatory status varies globally, with ongoing research into its broader therapeutic potential.

Mechanism of Action

Allopregnanolone acts primarily on the GABA-A receptor as a positive allosteric modulator. This interaction enhances the inhibitory effects of GABA, leading to increased neuronal inhibition and a calming effect on the brain, which is beneficial in treating mood disorders.

Molecular Data

FormulaC21H34O2
Molecular Weight318.5 g/mol
CAS Number516-54-1
PubChem CID92786

Half-Life & Pharmacokinetics

EndogenousCirculating half-life ~70 minutes
Intravenous~9 hours
OralPoor bioavailability due to first-pass metabolism

Intravenous administration is the primary clinical route due to poor oral bioavailability.

Storage

Temperature

Store at room temperature (15-30°C)

Light

Protect from light

Form

Aqueous solution: use within specified time after opening

Notes

Ensure proper storage conditions to maintain stability and efficacy.

Solubility

Allopregnanolone is poorly soluble in water but soluble in ethanol and other organic solvents.

Legal Status

🇩🇪DE

Data limited

🇺🇸US

FDA approved for postpartum depression; prescription required.

🇦🇺AU

Data limited

🇬🇧UK

Data limited

Legal status information is provided for general reference only and may not reflect the most current regulatory changes. Always verify with official government sources before making any decisions.

8 Research Publications

Transformative Therapies for Depression: Postpartum Depression, Major Depressive Disorder, and Treatment-Resistant Depression.

Review

Annual review of medicine · 2025

Researchers observed that depressive disorders are a major global health issue, with a significant gap in effective treatments. They highlighted new medications like brexanolone and zuranolone for postpartum depression and the potential of psilocybin for treatment-resistant depression as promising advancements in mental health care.

  • Brexanolone and zuranolone are the first FDA-approved treatments for postpartum depression.
  • There is a notable gap between the prevalence of depression and effective treatment options.
  • Psilocybin shows potential for patients with treatment-resistant depression.
PubMed

Gut bacteria convert glucocorticoids into progestins in the presence of hydrogen gas.

Unknown

Cell · 2024

Researchers found that certain gut bacteria can convert steroids produced by the body into sex hormones, specifically progestins. They observed that this process is influenced by hydrogen gas produced by gut bacteria, which may play a role in regulating various bodily functions, especially during pregnancy.

  • Gut bacteria can transform biliary corticoids into progestins.
  • Hydrogen gas production by gut bacteria enhances this conversion.
  • Increased levels of bacterial progestins are found in pregnant women.
PubMed

Pharmacotherapies Targeting GABA-Glutamate Neurotransmission for Treatment-Resistant Depression.

Review

Pharmaceuticals (Basel, Switzerland) · 2023

Researchers observed that treatment-resistant depression (TRD) is a complex condition with varying definitions based on the number of failed treatments. They highlighted the need for new treatment approaches that target different brain chemicals, specifically GABA and glutamate, to help those who do not respond to standard therapies.

  • TRD lacks a clear definition, with studies varying on treatment failure criteria.
  • There is a growing concern among clinicians about TRD.
  • Novel treatments targeting GABA and glutamate may offer hope for patients with TRD.
PubMed

GABA

Review

Trends in pharmacological sciences · 2023

Researchers observed that our understanding of depression has changed significantly over the past 20 years. They found that both glutamate and GABA neurotransmitters play important roles in depression, leading to new FDA-approved treatments like esketamine and brexanolone that target these systems.

  • Understanding of depression has shifted from a focus on monoamines to include glutamate and GABA.
  • New treatments targeting glutamatergic and GABAergic systems have been approved by the FDA.
  • Esketamine and brexanolone are examples of these new treatments for depression.
PubMed

Progesterone - Friend or foe?

Review

Frontiers in neuroendocrinology · 2020

Researchers observed that progesterone, often overlooked compared to estradiol, plays significant roles in women's health, particularly in mood regulation. While its metabolite allopregnanolone shows promise for treating postpartum depression, it may also contribute to negative symptoms in women with premenstrual syndrome and premenstrual dysphoric disorder. More research is needed to fully understand both the benefits and risks of progesterone.

  • Progesterone and its metabolite allopregnanolone have important biological properties and functions.
  • Allopregnanolone may help treat postpartum depression.
  • Progesterone can also trigger negative symptoms in women with PMS and PMDD.
PubMed

Postpartum Depression: Identification and Treatment in the Clinic Setting.

Review

Obstetrics and gynecology clinics of North America · 2020

Researchers found that postpartum depression (PPD) affects up to 15% of women and can often be identified before delivery by assessing mental health history and stressors. They observed that various treatments, including medications and a new infusion therapy, have shown positive results in managing PPD. The Edinburgh Postnatal Depression Scale is a widely used tool for screening and is available in multiple languages.

  • PPD affects up to 15% of women.
  • Risk factors can be identified before delivery.
  • Various effective treatment options are available.
PubMed

Pharmaceutical Approval Update.

Unknown

P & T : a peer-reviewed journal for formulary management · 2019

Researchers observed that Sunosi tablets can help reduce excessive daytime sleepiness in people with narcolepsy or obstructive sleep apnea. They also found that Zulresso injection is effective for treating postpartum depression in adults, and Mayzent tablets are beneficial for adults with relapsing forms of multiple sclerosis.

  • Sunosi helps with excessive daytime sleepiness in narcolepsy or obstructive sleep apnea.
  • Zulresso is effective for postpartum depression in adults.
  • Mayzent is beneficial for adults with relapsing forms of multiple sclerosis.
PubMed

Brexanolone injection in post-partum depression: two multicentre, double-blind, randomised, placebo-controlled, phase 3 trials.

Human

Lancet (London, England) · 2018

Researchers found that brexanolone injection significantly reduced symptoms of post-partum depression compared to a placebo in two clinical trials. The treatment showed a rapid onset of action and lasting effects, suggesting it could be a valuable new option for women experiencing this condition.

  • Brexanolone injection led to a greater reduction in depression scores than placebo.
  • The treatment demonstrated quick effects within 60 hours.
  • Adverse events were reported but were generally manageable.
PubMed

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This page is for informational and research purposes only. All information is based on published scientific literature. Nothing on this page constitutes medical advice or replaces consultation with a qualified healthcare professional.