Haloperidol, sold under the brand name Haldol among others, is a typical antipsychotic medication. Haloperidol is used in the treatment of schizophrenia, tics in Tourette syndrome, mania in bipolar disorder, delirium, agitation, acute psychosis, and hallucinations from alcohol withdrawal. It may be used by mouth or injection into a muscle or a vein. Haloperidol typically works within 30 to 60 minutes. A long-acting formulation may be used as an injection every four weeks by people with schizophrenia or related illnesses, who either forget or refuse to take the medication by mouth.
The atypical antipsychotics (AAP), also known as second generation antipsychotics (SGAs) and serotonin–dopamine antagonists (SDAs), are a group of antipsychotic drugs largely introduced after the 1970s and used to treat psychiatric conditions. Some atypical antipsychotics have received regulatory approval for schizophrenia, bipolar disorder, irritability in autism, and as an adjunct in major depressive disorder.
Aripiprazole, sold under the brand names Abilify and Aristada, among others, is an atypical antipsychotic. It is primarily used in the treatment of schizophrenia, obsessive compulsive disorder (OCD), and bipolar disorder; other uses include as an add-on treatment in major depressive disorder, tic disorders, and irritability associated with autism. Aripiprazole is taken by mouth or via injection into a muscle. A Cochrane review found low-quality evidence of effectiveness in treating schizophrenia.
Mirtazapine, sold under the brand name Remeron amongst others, is an atypical tetracyclic antidepressant, and as such is used primarily to treat depression. Its effects may take up to four weeks, but can also manifest as early as one to two weeks. It is often used in cases of depression complicated by anxiety or insomnia. The effectiveness of mirtazapine is comparable to other commonly prescribed antidepressants. It is taken by mouth.
The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model that attributes the positive symptoms of schizophrenia to a disturbed and hyperactive dopaminergic signal transduction. The model draws evidence from the observation that a large number of antipsychotics have dopamine-receptor antagonistic effects. The theory, however, does not posit dopamine overabundance as a complete explanation for schizophrenia. Rather, the overactivation of D2 receptors, specifically, is one effect of the global chemical synaptic dysregulation observed in this disorder.
The mesocortical pathway is a dopaminergic pathway that connects the ventral tegmentum to the prefrontal cortex. It is one of the four major dopamine pathways in the brain. It is essential to the normal cognitive function of the dorsolateral prefrontal cortex, and is thought to be involved in cognitive control, motivation, and emotional response.
Amisulpride is an antiemetic and antipsychotic medication used at lower doses intravenously to prevent and treat postoperative nausea and vomiting; and at higher doses by mouth to treat schizophrenia and acute psychotic episodes. It is sold under the brand names Barhemsys and Solian, Socian, Deniban and others. At very low doses it is also used to treat dysthymia.
The 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor (GPCR). The 5-HT2A receptor is a cell surface receptor, but has several intracellular locations. 5-HT is short for 5-hydroxy-tryptamine or serotonin. This is the main excitatory receptor subtype among the GPCRs for serotonin, although 5-HT2A may also have an inhibitory effect on certain areas such as the visual cortex and the orbitofrontal cortex. This receptor was first noted for its importance as a target of serotonergic psychedelic drugs such as LSD and psilocybin mushrooms. Later it came back to prominence because it was also found to be mediating, at least partly, the action of many antipsychotic drugs, especially the atypical ones.
Flibanserin, sold under the brand name Addyi, is a medication approved for the treatment of pre-menopausal women with hypoactive sexual desire disorder (HSDD). The medication improves sexual desire, increases the number of satisfying sexual events, and decreases the distress associated with low sexual desire. The most common side effects are dizziness, sleepiness, nausea, difficulty falling asleep or staying asleep and dry mouth.
Desmetramadol, also known as O-desmethyltramadol (O-DSMT), is an opioid analgesic and the main active metabolite of tramadol. Tramadol is demethylated by the liver enzyme CYP2D6 to desmetramadol in the same way as codeine, and so similarly to the variation in effects seen with codeine, individuals who have a less active form of CYP2D6 will tend to have reduced analgesic effects from tramadol. Because desmetramadol itself does not need to be metabolized to induce an analgesic effect, it can be used in individuals with low CYP2D6 activity unlike tramadol.
The glutamate hypothesis of schizophrenia models the subset of pathologic mechanisms of schizophrenia linked to glutamatergic signaling. The hypothesis was initially based on a set of clinical, neuropathological, and, later, genetic findings pointing at a hypofunction of glutamatergic signaling via NMDA receptors. While thought to be more proximal to the root causes of schizophrenia, it does not negate the dopamine hypothesis, and the two may be ultimately brought together by circuit-based models. The development of the hypothesis allowed for the integration of the GABAergic and oscillatory abnormalities into the converging disease model and made it possible to discover the causes of some disruptions.
Medifoxamine, previously sold under the brand names Clédial and Gerdaxyl, is an atypical antidepressant with additional anxiolytic properties acting via dopaminergic and serotonergic mechanisms which was formerly marketed in France and Spain, as well as Morocco. The drug was first introduced in France sometime around 1990. It was withdrawn from the market in 1999 (Morocco) and 2000 (France) following incidences of hepatotoxicity.
Pimavanserin, sold under the brand name Nuplazid, is an atypical antipsychotic which is approved for the treatment of Parkinson's disease psychosis and is also being studied for the treatment of Alzheimer’s disease psychosis, schizophrenia, agitation, and major depressive disorder. Unlike other antipsychotics, pimavanserin is not a dopamine receptor antagonist.
Pomaglumetad (LY-404,039) is an amino acid analog drug that acts as a highly selective agonist for the metabotropic glutamate receptor group II subtypes mGluR2 and mGluR3. Pharmacological research has focused on its potential antipsychotic and anxiolytic effects. Pomaglumetad is intended as a treatment for schizophrenia and other psychotic and anxiety disorders by modulating glutamatergic activity and reducing presynaptic release of glutamate at synapses in limbic and forebrain areas relevant to these disorders. Human studies investigating therapeutic use of pomaglumetad have focused on the prodrug LY-2140023, a methionine amide of pomaglumetad (also called pomaglumetad methionil) since pomaglumetad exhibits low oral absorption and bioavailability in humans.
Norepinephrine and dopamine disinhibitors (NDDIs) are a class of drugs which act at specific sites to disinhibit downstream norepinephrine and dopamine release in the brain.
N-Desmethylclozapine (NDMC), or norclozapine, is a major active metabolite of the atypical antipsychotic drug clozapine. Unlike clozapine, it possesses intrinsic activity at the D2/D3 receptors, and acts as a weak partial agonist at these sites similarly to aripiprazole and bifeprunox. Notably, NDMC has also been shown to act as a potent and efficacious agonist at the M1 and δ-opioid receptors, unlike clozapine as well. It was hypothesized that on account of these unique actions, NDMC might underlie the clinical superiority of clozapine over other antipsychotics. However, clinical trials found NMDC itself ineffective in the treatment of schizophrenia. This may be because it possesses relatively low D2/D3 occupancy compared to 5-HT2 (<15% versus 64-79% at a dose of 10–60 mg/kg s.c. in animal studies). Albeit not useful in the treatment of positive symptoms on its own, it cannot be ruled out that NDMC may contribute to the efficacy of clozapine on cognitive and/or negative symptoms.
Cariprazine, sold under the brand names Vraylar and Reagila among others, is an atypical antipsychotic originated by Gedeon Richter, which is used in the treatment of schizophrenia, bipolar mania, bipolar depression, and major depressive disorder. It acts primarily as a D3 and D2 receptor partial agonist, with a preference for the D3 receptor. Cariprazine is also a partial agonist at the serotonin 5-HT1A receptor and acts as an antagonist at 5-HT2B and 5-HT2A receptors, with high selectivity for the D3 receptor. It is taken by mouth.
F-15,063 is an orally active potential antipsychotic, and an antagonist at the D2/D3 receptors, partial agonist at the D4 receptor, and agonist at the 5-HT1A receptors. It has greater efficacy at the 5-HT1A receptors than other antipsychotics, such as clozapine, aripiprazole, and ziprasidone. This greater efficacy may lead to enhanced antipsychotic properties, as antipsychotics that lack 5-HT1A affinity are associated with increased risk of extrapyramidal symptoms, and lack of activity against the negative symptoms of schizophrenia.
5-HT2C receptor agonists are a class of drugs that activate 5-HT2C receptors. They have been investigated for the treatment of a number of conditions including obesity, psychiatric disorders, sexual dysfunction and urinary incontinence.
Brilaroxazine, also known as oxaripiprazole, is an investigational atypical antipsychotic which is under development by Reviva Pharmaceuticals for the treatment of neuropsychiatric and inflammatory disorders. As of July 2023, it is in phase III clinical trials for schizophrenia. Reviva Pharmaceuticals also intends to investigate brilaroxazine for the treatment of bipolar disorder, major depressive disorder, attention deficit hyperactivity disorder (ADD/ADHD), psychosis/agitation associated with Alzheimer's disease, Parkinson's disease psychosis, as well as the inflammatory disorders pulmonary arterial hypertension (PAH), idiopathic pulmonary fibrosis (IPF), and psoriasis. The FDA granted brilaroxazine orphan drug designation for the treatment of PAH and IPF.
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