Zolpidem, sold under the brand name Ambien among others, is a medication primarily used for the short-term treatment of sleeping problems. Guidelines recommend that it be used only after cognitive behavioral therapy for insomnia and behavioral changes, such as sleep hygiene, have been tried. It decreases the time to sleep onset by about fifteen minutes and at larger doses helps people stay asleep longer. It is taken by mouth and is available in conventional tablets, sublingual tablets, or oral spray.
The GABAA receptor (GABAAR) is an ionotropic receptor and ligand-gated ion channel. Its endogenous ligand is γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the central nervous system.Accurate regulation of GABAergic transmission through appropriate developmental processes, specificity to neural cell types, and responsiveness to activity is crucial for the proper functioning of nearly all aspects of the central nervous system (CNS). Upon opening, the GABAA receptor on the postsynaptic cell is selectively permeable to chloride ions (Cl−) and, to a lesser extent, bicarbonate ions (HCO3−).
Neurosteroids, also known as neuroactive steroids, are endogenous or exogenous steroids that rapidly alter neuronal excitability through interaction with ligand-gated ion channels and other cell surface receptors. The term neurosteroid was coined by the French physiologist Étienne-Émile Baulieu and refers to steroids synthesized in the brain. The term, neuroactive steroid refers to steroids that can be synthesized in the brain, or are synthesized by an endocrine gland, that then reach the brain through the bloodstream and have effects on brain function. The term neuroactive steroids was first coined in 1992 by Steven Paul and Robert Purdy. In addition to their actions on neuronal membrane receptors, some of these steroids may also exert effects on gene expression via nuclear steroid hormone receptors. Neurosteroids have a wide range of potential clinical applications from sedation to treatment of epilepsy and traumatic brain injury. Ganaxolone, a synthetic analog of the endogenous neurosteroid allopregnanolone, is under investigation for the treatment of epilepsy.
Alpidem, sold under the brand name Ananxyl, is a nonbenzodiazepine anxiolytic medication which was briefly used to treat anxiety disorders but is no longer marketed. It was previously marketed in France, but was discontinued due to liver toxicity. Alpidem is taken by mouth.
Bretazenil (Ro16-6028) is an imidazopyrrolobenzodiazepine anxiolytic drug which is derived from the benzodiazepine family, and was invented in 1988. It is most closely related in structure to the GABA antagonist flumazenil, although its effects are somewhat different. It is classified as a high-potency benzodiazepine due to its high affinity binding to benzodiazepine binding sites where it acts as a partial agonist. Its profile as a partial agonist and preclinical trial data suggests that it may have a reduced adverse effect profile. In particular bretazenil has been proposed to cause a less strong development of tolerance and withdrawal syndrome. Bretazenil differs from traditional 1,4-benzodiazepines by being a partial agonist and because it binds to α1, α2, α3, α4, α5 and α6 subunit containing GABAA receptor benzodiazepine receptor complexes. 1,4-benzodiazepines bind only to α1, α2, α3 and α5GABAA benzodiazepine receptor complexes.
Allopregnanolone is a naturally occurring neurosteroid which is made in the body from the hormone progesterone. As a medication, allopregnanolone is referred to as brexanolone, sold under the brand name Zulresso, and used to treat postpartum depression. It is given by injection into a vein.
Valerenic acid is a sesquiterpenoid constituent of the essential oil of the valerian plant.
Etifoxine, sold under the trade name Stresam among others, is a nonbenzodiazepine anxiolytic agent, primarily indicated for short-term management of adjustment disorder, specifically instances of situational depression accompanied by anxiety, such as stress-induced anxiety. Administration is by mouth. Side effects associated with etifoxine use include slight drowsiness, headache, skin eruptions, and allergic reactions. In rare cases, etifoxine has been linked to severe skin and liver toxicity, as well as menstrual bleeding between periods. Unlike benzodiazepines, etifoxine does not cause sedation or lack of coordination. Etifoxine acts as a GABAA receptor positive allosteric modulator and as a ligand for translocator proteins. Both mechanisms are conjectured to contribute to its anxiolytic properties.
L-838,417 is an anxiolytic drug used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic. The compound was developed by Merck, Sharp and Dohme.
SL651498 is an anxiolytic and anticonvulsant drug used in scientific research, with a chemical structure most closely related to β-carboline derivatives such as abecarnil and gedocarnil. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic.
ELB-139 (LS-191,811) is an anxiolytic drug with a novel chemical structure, which is used in scientific research. It has similar effects to benzodiazepine drugs, but is structurally distinct and so is classed as a nonbenzodiazepine anxiolytic.
L-655,708 (FG-8094) is a nootropic drug invented in 1996 by a team working for Merck, Sharp and Dohme, that was the first compound developed which acts as a subtype-selective inverse agonist at the α5 subtype of the benzodiazepine binding site on the GABAA receptor. It acts as an inverse agonist at the α1, α2, α3 and α5 subtypes, but with much higher affinity for α5, and unlike newer α5 inverse agonists such as α5IA, L-655,708 exerts its subtype selectivity purely via higher binding affinity for this receptor subtype, with its efficacy as an inverse agonist being around the same at all the subtypes it binds to.
In pharmacology, GABAA receptor positive allosteric modulators, also known as GABAkines or GABAA receptor potentiators, are positive allosteric modulator (PAM) molecules that increase the activity of the GABAA receptor protein in the vertebrate central nervous system.
Isopregnanolone, also known as isoallopregnanolone and epiallopregnanolone, as well as sepranolone (INN), and as 3β-hydroxy-5α-pregnan-20-one or 3β,5α-tetrahydroprogesterone (3β,5α-THP), is an endogenous neurosteroid and a natural 3β-epimer of allopregnanolone. It has been reported to act as a subunit-selective negative allosteric modulator of the GABAA receptor, and antagonizes in animals and humans some but not all of the GABAA receptor-mediated effects of allopregnanolone, such as anesthesia, sedation, and reduced saccadic eye movements, but not learning impairment. Isopregnanolone has no hormonal effects and appears to have no effect on the GABAA receptor by itself; it selectively antagonizes allopregnanolone and does not affect the effects of other types of GABAA receptor positive allosteric modulators such as benzodiazepines or barbiturates.
EVT-201 is a benzodiazepine derivative drug and partial positive allosteric modulator of the benzodiazepine site of the GABAA receptor. It has 2–4-fold higher functional affinity for the α1 subunit relative to the α2, α3, and α5 subunits and significantly less intrinsic activity in comparison to currently-marketed benzodiazepines and the Z-drugs. Despite the lower efficacy, EVT-201 still shows effectiveness in the treatment of insomnia, and it is thought that the lower efficacy may result in fewer side effects, such as motor incoordination. The drug was originally developed by Roche, based on preclinical data, as a non-sedating anxiolytic, but was found to produce sedation in humans in phase I clinical trials. For this reason, it was subsequently licensed to Evotec, which is now developing it for the treatment of insomnia. As of 2007, EVT-201 has completed phase II clinical trials for this indication, with positive findings reported. As of August 2015, Phase II development is ongoing in China.
Basmisanil is a highly selective inverse agonist/negative allosteric modulator of α5 subunit-containing GABAA receptors which is under development by Roche for the treatment of cognitive impairment associated with Down syndrome. As of June 2016, it is no longer studied. It is studied with schizophrenia patients.
Zuranolone, sold under the brand name Zurzuvae, is a medication used for the treatment of postpartum depression. It is taken by mouth.
GL-II-73 (GL-ii-073) is a benzodiazepine derivative related in chemical structure to compounds such as midazolam and adinazolam. It is described as an α5 preferring positive allosteric modulator of the benzodiazepine site of GABAA receptors, with weaker activity at α2 and α3 and no significant affinity for the α1 subtype. In animal tests it was found to produce effects consistent with antidepressant, anxiolytic and nootropic actions.
Deuterated etifoxine is a deuterated drug which is under development for the treatment of anxiety disorders and mood disorders. It was originated by GABA Therapeutics and is under development by GABA Therapeutics and ATAI Life Sciences. Deuterated etifoxine is a deuterated form of etifoxine (Stresam) with improved pharmacokinetic properties, for instance a longer elimination half-life and duration of action. Etifoxine has been widely used as an anxiolytic for many decades. Etifoxine and deuterated etifoxine are GABAA receptor positive allosteric modulators (GABAkines) and ligands of the translocator protein (TSPO), both of which may contribute to anxiolytic effects. The TSPO promotes steroidogenesis of inhibitory neurosteroids such as allopregnanolone, which act as potent GABAA receptor positive allosteric modulators, and hence interactions with the TSPO can also indirectly potentiate the GABAA receptor. The precise isotopic substitution of deuterated etifoxine has not yet been disclosed. As of January 2023, deuterated etifoxine is in phase 1 clinical trials for anxiety disorders and preclinical development for mood disorders.
