Flumazenil is a selective GABAA receptor antagonist administered via injection, otic insertion, or intranasally. Therapeutically, it acts as both an antagonist and antidote to benzodiazepines, through competitive inhibition.
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 and, to a lesser extent, bicarbonate ions.
Clobazam, sold under the brand names Frisium, Onfi and others, is a benzodiazepine class medication that was patented in 1968. Clobazam was first synthesized in 1966 and first published in 1969. Clobazam was originally marketed as an anxioselective anxiolytic since 1970, and an anticonvulsant since 1984. The primary drug-development goal was to provide greater anxiolytic, anti-obsessive efficacy with fewer benzodiazepine-related side effects.
Clomethiazole is a sedative and hypnotic originally developed by Hoffmann-La Roche in the 1930s. The drug is used in treating and preventing symptoms of acute alcohol withdrawal.
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.
Pagoclone is an anxiolytic agent from the cyclopyrrolone family, related to better-known drugs such as the sleeping medication zopiclone. It was synthesized by a French team working for Rhone-Poulenc & Rorer S.A. Pagoclone belongs to the class of nonbenzodiazepines, which have similar effects to the older benzodiazepine group, but with quite different chemical structures. It was never commercialised.
DMCM is a drug from the β-carboline family that induces anxiety and convulsions by acting as a negative allosteric modulator of GABAA receptors — functionally opposite to benzodiazepines and related drugs which are positive allosteric modulators — and is used in scientific research for these properties to test new anxiolytic and anticonvulsant medications, respectively. It has also been shown to produce analgesic effects in animals, which is thought to be the drug's induced panic reducing the perception of pain.
Fenobam is an imidazole derivative developed by McNeil Laboratories in the late 1970s as a novel anxiolytic drug with an at-the-time-unidentified molecular target in the brain. Subsequently, it was determined that fenobam acts as a potent and selective negative allosteric modulator of the metabotropic glutamate receptor subtype mGluR5, and it has been used as a lead compound for the development of a range of newer mGluR5 antagonists.
Pipequaline (INN) is an anxiolytic drug that was never marketed. It possesses a novel chemical structure that is not closely related to other drugs of this type. The drug has a similar pharmacological profile to the benzodiazepine family of drugs, but with mainly anxiolytic properties and very little sedative, amnestic or anticonvulsant effects, and so is classified as a nonbenzodiazepine anxiolytic.
Loreclezole is a sedative and an anticonvulsant which acts as a GABAA receptor positive allosteric modulator. The binding site of loreclezole has been shown experimentally to be shared by valerenic acid, an extract of the root of the valerian plant. Structurally, loreclezole is a triazole derivative. In animal seizure models, loreclezole is protective against pentylenetetrazol seizures but is less active in the maximal electroshock test. In addition, at low, nontoxic doses, the drug has anti-absence activity in a genetic model of generalized absence epilepsy. Consequently, loreclezole has a profile of activity similar to that of benzodiazepines. A potential benzodiazepine-like interaction with GABA receptors is suggested by the observation that the anticonvulsant effects of loreclezole can be reversed by benzodiazepine receptor inverse agonists. The benzodiazepine antagonist flumazenil, however, fails to alter the anticonvulsant activity of loreclezole, indicating that loreclezole is not a benzodiazepine receptor agonist. Using native rat and cloned human GABA-A receptors, loreclezole strongly potentiated GABA-activated chloride current. However, the activity of the drug did not require the presence of the γ-subunit and was not blocked by flumazenil, confirming that loreclezole does not interact with the benzodiazepine recognition site.
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.
Y-23684 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.
CGP-37849 is a competitive antagonist at the NMDA receptor. It is a potent, orally active anticonvulsant in animal models, and was researched for the treatment of epilepsy. It also has neuroprotective activity and shows antidepressant and anxiolytic effects.
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.
TPA-023 (MK-0777) 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. It is a mixed, subtype-selective ligand of the benzodiazepine site of α1, α2, α3, and α5-containing GABAA receptors, where it acts as a partial agonist at benzodiazepine sites of the α2 and α3-containing subtypes, but as a silent antagonist at α1 and α5-containing subtypes. It has primarily anxiolytic and anticonvulsant effects in animal tests, but with no sedative effects even at 50 times the effective anxiolytic dose.
TP-13 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. It is a subtype-selective partial agonist at GABAA receptors, binding selectively to GABAA receptor complexes bearing α2 and α3 subunits. It has modest anticonvulsant activity although less than that of diazepam, and its main effect is likely to be selective anxiolytic action, as seen with other related α2/3-preferring agonists such as L-838,417.
TP-003 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. It is a positive allosteric modulator at the benzodiazepine binding site of GABAA receptors. It has modest anticonvulsant activity although less than that of diazepam.
FGIN-1-27 is an anxiolytic drug which acts as a selective agonist at the peripheral benzodiazepine receptor, also known as the mitochondrial 18 kDa translocator protein or TSPO. It is thought to produce anxiolytic effects by stimulating steroidogenesis of neuroactive steroids such as allopregnanolone.
