Benzodiazepines, colloquially known as "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.
Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants. TCAs were discovered in the early 1950s and were marketed later in the decade. They are named after their chemical structure, which contains three rings of atoms. Tetracyclic antidepressants (TeCAs), which contain four rings of atoms, are a closely related group of antidepressant compounds.
Naloxone, sold under the brand name Narcan among others, is an opioid antagonist, a medication used to reverse or reduce the effects of opioids. For example, it is used to restore breathing after an opioid overdose. Effects begin within two minutes when given intravenously, five minutes when injected into a muscle, and ten minutes as a nasal spray. Naloxone blocks the effects of opioids for 30 to 90 minutes.
Azapirones are a class of drugs used as anxiolytics, antidepressants, and antipsychotics. They are commonly used as add-ons to other antidepressants, such as selective serotonin reuptake inhibitors (SSRIs).
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.
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.
Adinazolam is a tranquilizer of the triazolobenzodiazepine (TBZD) class, which are benzodiazepines (BZDs) fused with a triazole ring. It possesses anxiolytic, anticonvulsant, sedative, and antidepressant properties. Adinazolam was developed by Jackson B. Hester, who was seeking to enhance the antidepressant properties of alprazolam, which he also developed. Adinazolam was never FDA approved and never made available to the public market; however, it has been sold as a designer drug.
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.
Siramesine is a sigma receptor agonist, selective for the σ2 subtype. In animal studies, siramesine has been shown to produce anxiolytic and antidepressant effects. It was developed by the pharmaceutical company H Lundbeck for the treatment of anxiety, although development was discontinued after clinical trials showed a lack of efficacy in humans. Siramesine has been shown to produce an enhanced antidepressant effect when co-administered with NMDA antagonists. It has also been used to study the σ2 activity of cocaine, and has been shown to produce anticancer properties both in vitro and in vivo.
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.
ZK-93423 is an anxiolytic drug from the β-Carboline family, closely related to abecarnil. It is a nonbenzodiazepine GABAA agonist which is not subtype selective and stimulates α1, α2, α3, and α5-subunit containing GABAA receptors equally. It has anticonvulsant, muscle relaxant and appetite stimulating properties comparable to benzodiazepine drugs. ZK-93423 has also been used as a base to develop new and improved beta-carboline derivatives and help map the binding site of the GABAA receptor.
Ro5-4864 (4'-chlorodiazepam) is a drug which is a benzodiazepine derivative of diazepam. However unlike most benzodiazepine derivatives, Ro5-4864 lacks affinity for GABAA receptors and lacks typical benzodiazepine effects, instead being sedative yet also convulsant and anxiogenic in effects. Ro5-4864 was found to be a potent ligand for the "peripheral benzodiazepine receptor", later renamed to mitochondrial translocator protein 18kDa (TSPO). Despite its convulsant effects, at lower doses Ro5-4864 has proved to be neuroprotective and has become widely used for research into the role of the TSPO protein in neurotoxicity. In vitro studies and rodent models also suggest the possibility of analgesic, antidepressant, cardioprotective, and anti-cancer effects.
Pentylenetetrazol (PTZ), also known as pentylenetetrazole, leptazol, metrazol, pentetrazol (INN), pentamethylenetetrazol, Corazol, Cardiazol, or Deumacard, is a drug formerly used as a circulatory and respiratory stimulant. High doses cause convulsions, as discovered by Hungarian-American neurologist and psychiatrist Ladislas J. Meduna in 1934. It has been used in convulsive therapy, and was found to be effective—primarily for depression—but side effects such as uncontrolled seizures were difficult to avoid. In 1939, pentylenetetrazol was replaced by electroconvulsive therapy, which is easier to administer, as the preferred method for inducing seizures in England's mental hospitals. In the US, its approval by the Food and Drug Administration was revoked in 1982. It is used in Italy as a cardio-respiratory stimulant in combination with codeine in a cough suppressant drug.
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.
Fasedienol, also known as 4-androstadienol or as 4,16-androstadien-3β-ol, is a pherine which is under development by VistaGen Therapeutics in a nasal spray formulation (PRN) for the acute treatment of social anxiety disorder. It is also being investigated by VistaGen Therapeutics for the treatment of generalized anxiety disorder (GAD) and post-traumatic stress disorder (PTSD). The pherine is a positional isomer of the endogenous pheromone androstadienol. As of 2020, it is in phase III clinical trials for social anxiety disorder.
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.
