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Benzodiazepines, colloquially called "benzos", are a class of depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat conditions such as anxiety disorders, insomnia, and seizures. The first benzodiazepine, chlordiazepoxide (Librium), was discovered accidentally by Leo Sternbach in 1955, and was made available in 1960 by Hoffmann–La Roche, which followed with the development of diazepam (Valium) three years later, in 1963. By 1977, benzodiazepines were the most prescribed medications globally; the introduction of selective serotonin reuptake inhibitors (SSRIs), among other factors, decreased rates of prescription, but they remain frequently used worldwide.
Diazepam, sold under the brand name Valium among others, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is used to treat a range of conditions, including anxiety, seizures, alcohol withdrawal syndrome, muscle spasms, insomnia, and restless legs syndrome. It may also be used to cause memory loss during certain medical procedures. It can be taken orally, as a suppository inserted into the rectum, intramuscularly, intravenously or used as a nasal spray. When injected intravenously, effects begin in one to five minutes and last up to an hour. When taken by mouth, effects begin after 15 to 60 minutes.
A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of receptor proteins. They are sometimes called blockers; examples include alpha blockers, beta blockers, and calcium channel blockers. In pharmacology, antagonists have affinity but no efficacy for their cognate receptors, and binding will disrupt the interaction and inhibit the function of an agonist or inverse agonist at receptors. Antagonists mediate their effects by binding to the active site or to the allosteric site on a receptor, or they may interact at unique binding sites not normally involved in the biological regulation of the receptor's activity. Antagonist activity may be reversible or irreversible depending on the longevity of the antagonist–receptor complex, which, in turn, depends on the nature of antagonist–receptor binding. The majority of drug antagonists achieve their potency by competing with endogenous ligands or substrates at structurally defined binding sites on receptors.
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 (Cl−) and, to a lesser extent, bicarbonate ions (HCO3−).
A selective progesterone receptor modulator (SPRM) is an agent that acts on the progesterone receptor (PR), the biological target of progestogens like progesterone. A characteristic that distinguishes such substances from full receptor agonists and full antagonists is that their action differs in different tissues, i.e. agonist in some tissues while antagonist in others. This mixed profile of action leads to stimulation or inhibition in tissue-specific manner, which further raises the possibility of dissociating undesirable adverse effects from the development of synthetic PR-modulator drug candidates.
Nordazepam is a 1,4-benzodiazepine derivative. Like other benzodiazepine derivatives, it has amnesic, anticonvulsant, anxiolytic, muscle relaxant, and sedative properties. However, it is used primarily in the treatment of anxiety disorders. It is an active metabolite of diazepam, chlordiazepoxide, clorazepate, prazepam, pinazepam, and medazepam.
Camazepam is a benzodiazepine psychoactive drug, marketed under the brand names Albego, Limpidon and Paxor. It is the dimethyl carbamate ester of temazepam, a metabolite of diazepam. While it possesses anxiolytic, anticonvulsant, skeletal muscle relaxant and hypnotic properties it differs from other benzodiazepines in that its anxiolytic properties are particularly prominent but has comparatively limited anticonvulsant, hypnotic and skeletal muscle relaxant properties.
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.
An anxiogenic or panicogenic substance is one that causes anxiety. This effect is in contrast to anxiolytic agents, which inhibits anxiety. Together these categories of psychoactive compounds may be referred to as anxiotropic compounds.
NMDA receptor antagonists are a class of drugs that work to antagonize, or inhibit the action of, the N-Methyl-D-aspartate receptor (NMDAR). They are commonly used as anesthetics for humans and non-human animals; the state of anesthesia they induce is referred to as dissociative anesthesia.
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.
Ro15-4513(IUPAC: Ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo-1,4-benzodiazepine-3-carboxylate) is a weak partial inverse agonist of the benzodiazepine class of drugs, developed by Hoffmann–La Roche in the 1980s. It acts as an inverse agonist, and can therefore be an antidote to the acute impairment caused by alcohols, including ethanol, isopropanol, tert-butyl alcohol, tert-amyl alcohol, 3-methyl-3-pentanol, methylpentynol and ethchlorvynol.
Imidazenil is an experimental anxiolytic drug which is derived from the benzodiazepine family, and is most closely related to other imidazobenzodiazepines such as midazolam, flumazenil, and bretazenil.
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.
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.
In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimuli. Some of them, like benzodiazepines or alcohol, function as psychoactive drugs. The site that an allosteric modulator binds to is not the same one to which an endogenous agonist of the receptor would bind. Modulators and agonists can both be called receptor ligands.
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.
References
- ↑ Cortelli, P.; Avallone, R.; Baraldi, M.; Zeneroli, ML.; Mandrioli, J.; Corsi, L.; Riva, R.; Tinuper, P.; et al. (Dec 2005). "Endozepines in recurrent stupor". Sleep Med Rev. 9 (6): 477–87. doi:10.1016/j.smrv.2005.07.003. PMID 16233983.
- ↑ Farzampour, Z; Reimer, RJ; Huguenard, J (2015). "Endozepines". Diversity and Functions of GABA Receptors: A Tribute to Hanns Möhler, Part A. Advances in Pharmacology (San Diego, Calif.). Vol. 72. pp. 147–64. doi:10.1016/bs.apha.2014.10.005. ISBN 9780128026601. PMC 4550098 . PMID 25600369.