Anticonvulsants are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder and borderline personality disorder, since many seem to act as mood stabilizers, and for the treatment of neuropathic pain. Anticonvulsants suppress the excessive rapid firing of neurons during seizures. Anticonvulsants also prevent the spread of the seizure within the brain.
Diazepam, first marketed as Valium, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is commonly 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 by mouth, inserted into the rectum, injected into muscle, injected into a vein or used as a nasal spray. When given into a vein, effects begin in one to five minutes and last up to an hour. By mouth, effects begin after 15 to 60 minutes.
Depressants, or central depressants, are drugs that lower neurotransmission levels, which is to depress or reduce arousal or stimulation in various areas of the brain. Depressants are also colloquially referred to as "downers" as they lower the level of arousal when taken. Stimulants, or "uppers," increase mental or physical function, hence the opposite drug class from depressants is stimulants, not antidepressants.
Clonazepam, sold under the brand names Klonopin and Rivotril, is a medication used to prevent and treat seizures, panic disorder, anxiety disorders, and the movement disorder known as akathisia. It is a tranquilizer of the benzodiazepine class. It possesses anxiolytic, anticonvulsant, sedative, hypnotic, and skeletal muscle relaxant properties. It is typically taken by mouth. Effects begin within one hour and last between six and twelve hours.
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. Upon opening, the GABAA receptor on the postsynaptic cell is selectively permeable to chloride ions (Cl−) and, to a lesser extent, bicarbonate ions (HCO3−). Depending on the membrane potential and the ionic concentration difference, this can result in ionic fluxes across the pore. If the membrane potential is higher than the equilibrium potential (also known as the reversal potential) for chloride ions, when the receptor is activated Cl− will flow into the cell. This causes an inhibitory effect on neurotransmission by diminishing the chance of a successful action potential occurring at the postsynaptic cell. The reversal potential of the GABAA-mediated inhibitory postsynaptic potential (IPSP) in normal solution is −70 mV, contrasting the GABAB IPSP (-100 mV).
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.
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.
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 a 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.
A GABA receptor agonist is a drug that is an agonist for one or more of the GABA receptors, producing typically sedative effects, and may also cause other effects such as anxiolytic, anticonvulsant, and muscle relaxant effects. There are three receptors of the gamma-aminobutyric acid. The two receptors GABA-α and GABA-ρ are ion channels that are permeable to chloride ions which reduces neuronal excitability. The GABA-β receptor belongs to the class of G-Protein coupled receptors that inhibit adenylyl cyclase, therefore leading to decreased cyclic adenosine monophosphate (cAMP). GABA-α and GABA-ρ receptors produce sedative and hypnotic effects and have anti-convulsion properties. GABA-β receptors also produce sedative effects. Furthermore, they lead to changes in gene transcription.
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.
γ-Amino-β-hydroxybutyric acid (GABOB), also known as β-hydroxy-γ-aminobutyric acid (β-hydroxy-GABA), and sold under the brand name Gamibetal among others, is an anticonvulsant which is used for the treatment of epilepsy in Europe, Japan, and Mexico. It is a GABA analogue, or an analogue of the neurotransmitter γ-aminobutyric acid (GABA), and has been found to be an endogenous metabolite of GABA.
Gamma-aminobutyric acid receptor subunit gamma-2 is a protein that in humans is encoded by the GABRG2 gene.
Gamma-aminobutyric acid receptor subunit alpha-1 is a protein that in humans is encoded by the GABRA1 gene.
Gamma-aminobutyric acid receptor subunit beta-3 is a protein that in humans is encoded by the GABRB3 gene. It is located within the 15q12 region in the human genome and spans 250kb. This gene includes 10 exons within its coding region. Due to alternative splicing, the gene codes for many protein isoforms, all being subunits in the GABAA receptor, a ligand-gated ion channel. The beta-3 subunit is expressed at different levels within the cerebral cortex, hippocampus, cerebellum, thalamus, olivary body and piriform cortex of the brain at different points of development and maturity. GABRB3 deficiencies are implicated in many human neurodevelopmental disorders and syndromes such as Angelman syndrome, Prader-Willi syndrome, nonsyndromic orofacial clefts, epilepsy and autism. The effects of methaqualone and etomidate are mediated through GABBR3 positive allosteric modulation.
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.
A convulsant is a drug which induces convulsions and/or epileptic seizures, the opposite of an anticonvulsant. These drugs generally act as stimulants at low doses, but are not used for this purpose due to the risk of convulsions and consequent excitotoxicity. Most convulsants are antagonists at either the GABAA or glycine receptors, or ionotropic glutamate receptor agonists. Many other drugs may cause convulsions as a side effect at high doses but only drugs whose primary action is to cause convulsions are known as convulsants. Nerve agents such as sarin, which were developed as chemical weapons, produce convulsions as a major part of their toxidrome, but also produce a number of other effects in the body and are usually classified separately. Dieldrin which was developed as an insecticide blocks chloride influx into the neurons causing hyperexcitability of the CNS and convulsions. The Irwin observation test and other studies that record clinical signs are used to test the potential for a drug to induce convulsions. Camphor, and other terpenes given to children with colds can act as convulsants in children who have had febrile seizures.
FG-8205 (L-663,581) is an imidazobenzodiazepine derivative related to bretazenil, which acts as a partial agonist at GABAA receptors, with slight selectivity for the α1-containing subtype. In animal tests it has anxiolytic and anticonvulsant effects but with little sedation or ataxia produced.
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.
A GABAA receptor negative allosteric modulator is a negative allosteric modulator (NAM), or inhibitor, of the GABAA receptor, a ligand-gated ion channel of the major inhibitory neurotransmitter γ-aminobutyric acid (GABA). They are closely related and similar to GABAA receptor antagonists. The effects of GABAA receptor NAMs are functionally the opposite of those of GABAA receptor positive allosteric modulators (PAMs) like the benzodiazepines, barbiturates, and ethanol (alcohol). Non-selective GABAA receptor NAMs can produce a variety of effects including convulsions, neurotoxicity, and anxiety, among others.
