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.