# Amisulpride

Amisulpride, sold under the brand names Solian and Barhemsys, is a medication used in the treatment of schizophrenia, acute psychotic episodes, depression, and nausea and vomiting. It is specifically used at lower doses intravenously to prevent and treat postoperative nausea and vomiting; at low doses by mouth to treat depression; and at higher doses by mouth to treat psychosis.
It is usually classed with the atypical antipsychotics. Chemically it is a benzamide and like other benzamide antipsychotics, such as sulpiride, it is associated with a high risk of elevating blood levels of the lactation hormone, prolactin (thereby potentially causing the absence of the menstrual cycle, breast enlargement, even in males, breast milk secretion not related to breastfeeding, impaired fertility, impotence, breast pain, etc.), and a low risk, relative to the typical antipsychotics, of causing movement disorders.
Amisulpride is indicated for use in the United States in adults for the prevention of postoperative nausea and vomiting (PONV), either alone or in combination with an antiemetic of a different class; and to treat PONV in those who have received antiemetic prophylaxis with an agent of a different class or have not received prophylaxis.
Amisulpride is believed to work by blocking, or antagonizing, the dopamine D$_2$ receptor, reducing its signalling. The effectiveness of amisulpride in treating dysthymia and the negative symptoms of schizophrenia is believed to stem from its blockade of the presynaptic dopamine D$_2$ and D$_3$ autoreceptors. These presynaptic receptors regulate the release of dopamine into the synapse, so by blocking them amisulpride increases dopamine concentrations in the synapse. This increased dopamine concentration is theorized to act on dopamine D$_1$ receptors to relieve depressive symptoms (in dysthymia) and the negative symptoms of schizophrenia.
It was introduced by Sanofi-Aventis in the 1990s. Its patent expired by 2008, and generic formulations became available. It is marketed in all English-speaking countries except for Canada.

## Medical uses
### Schizophrenia

Although according to other studies it appears to have comparable efficacy to olanzapine in the treatment of schizophrenia, amisulpride augmentation, similarly to sulpiride augmentation, has been considered a viable treatment option (although this is based on low-quality evidence) in clozapine-resistant cases of schizophrenia. Another recent study concluded that amisulpride is an appropriate first-line treatment for the management of acute psychosis.

### Depression

Amisulpride is approved and used at low doses in the treatment of dysthymia and major depressive disorder. Whereas typical doses used in schizophrenia block postsynaptic dopamine D$_2$-like receptors and reduce dopaminergic neurotransmission, low doses of amisulpride preferentially block presynaptic dopamine D$_2$ and D$_3$ autoreceptors and thereby disinhibit dopamine release and enhance dopaminergic neurotransmission. A 2010 Cochrane review found that low-dose amisulpride was effective in the treatment of dysthymia. Likewise, a 2024 literature review found that low-dose amisulpride was effective for dysthymia. The drug is approved for depression specifically in Italy, Greece, and certain other European countries.

### Postoperative nausea and vomiting

Amisulpride is indicated for use in the United States in adults for the prevention of postoperative nausea and vomiting (PONV), either alone or in combination with an antiemetic of a different class; and to treat PONV in those who have received antiemetic prophylaxis with an agent of a different class or have not received prophylaxis.

### Available forms

Amisulpride is available in the form of 100, 200, and 400 mg oral tablets. In the United States, it is available in the form of a 5 mg/2 mL (2.5 mg/mL) solution for intravenous administration.

## Contraindications

Amisulpride's use is contraindicated in the following disease states and populations
* Pheochromocytoma
* Concomitant prolactin-dependent tumours e.g. prolactinoma, breast cancer
* Movement disorders (e.g. Parkinson's disease and dementia with Lewy bodies)
* Lactation
* Children before the onset of puberty
Neither is it recommended to use amisulpride in patients with hypersensitivities to amisulpride or the excipients found in its dosage form.

## Adverse effects
### Very Common (≥10% incidence)

* Extrapyramidal side effects (EPS; including dystonia, tremor, akathisia, parkinsonism).

### Common (≥1%, <10% incidence)

* Insomnia
* Somnolence
* Hypersalivation
* Nausea
* Headache
* Hyperactivity
* Vomiting
* Hyperprolactinaemia (which can lead to galactorrhoea, breast enlargement and tenderness, sexual dysfunction, etc.)
* Weight gain (produces less weight gain than chlorpromazine, clozapine, iloperidone, olanzapine, paliperidone, quetiapine, risperidone, sertindole, zotepine and more (although not statistically significantly) weight gain than haloperidol, lurasidone, ziprasidone and approximately as much weight gain as aripiprazole and asenapine)
* Anticholinergic side effects (although it does not bind to the muscarinic acetylcholine receptors and hence these side effects are usually quite mild) such as
    - constipation
    - dry mouth
    - disorder of accommodation
    - Blurred vision

### Rare (<1% incidence)

* Hyponatraemia
* Bradycardia
* Hypotension
* Palpitations
* Urticaria
* Seizures
* Mania
* Oculogyric crisis
* Tardive dyskinesia
* Blood dyscrasias such as leucopenia, neutropenia and agranulocytosis
* QT interval prolongation (in a recent meta-analysis of the safety and efficacy of 15 antipsychotic drugs amisulpride was found to have the 2nd highest effect size for causing QT interval prolongation)
Hyperprolactinaemia results from antagonism of the D$_2$ receptors located on the lactotrophic cells found in the anterior pituitary gland. Amisulpride has a high propensity for elevating plasma prolactin levels as a result of its poor blood–brain barrier penetrability and hence the resulting greater ratio of peripheral D$_2$ occupancy to central D$_2$ occupancy. This means that to achieve the sufficient occupancy (~60–80%) of the central D$_2$ receptors in order to elicit its therapeutic effects a dose must be given that is enough to saturate peripheral D$_2$ receptors including those in the anterior pituitary.

### Discontinuation

The British National Formulary recommends a gradual withdrawal when discontinuing antipsychotics to avoid acute withdrawal syndrome or rapid relapse. Symptoms of withdrawal commonly include nausea, vomiting, and loss of appetite. Other symptoms may include restlessness, increased sweating, and trouble sleeping. Less commonly there may be a feeling of the world spinning, numbness, or muscle pains. Symptoms generally resolve after a short period of time.
There is tentative evidence that discontinuation of antipsychotics can result in psychosis. It may also result in reoccurrence of the condition that is being treated. Rarely tardive dyskinesia can occur when the medication is stopped.

## Overdose

Torsades de pointes is common in overdose. Amisulpride is moderately dangerous in overdose (with the TCAs being very dangerous and the SSRIs being modestly dangerous).

## Interactions

Amisulpride should not be used in conjunction with drugs that prolong the QT interval (such as citalopram, bupropion, clozapine, tricyclic antidepressants, sertindole, ziprasidone, etc.), reduce heart rate and those that can induce hypokalaemia. Likewise it is imprudent to combine antipsychotics due to the additive risk for tardive dyskinesia and neuroleptic malignant syndrome.

## Pharmacology
### Pharmacodynamics

Amisulpride :
| Site | K$_i$ (nM) | Species |
| SERTTooltip Serotonin transporter | 10000+ | Human |
| NETTooltip Norepinephrine transporter | 10000+ | Human |
| DATTooltip Dopamine transporter | 10000+ | Human |
| 5-HT$_{1A}$ | 10000+ | Human |
| 5-HT$_{1B}$ | 1744 | Human |
| 5-HT$_{1D}$ | 1341 | Human |
| 5-HT$_{1E}$ | 10000+ | Human |
| 5-HT$_{2A}$ | 8304 | Human |
| 5-HT$_{2B}$ | 13 | Human |
| 5-HT$_{2C}$ | 10000+ | Human |
| 5-HT$_3$ | 10000+ | Human |
| 5-HT$_{5A}$ | 10000+ | Human |
| 5-HT$_6$ | 4154 | Human |
| 5-HT$_7$ | 11.5 | Human |
| α$_{1A}$ | 10000+ | Human |
| α$_{1B}$ | 10000+ | Human |
| α$_{1D}$ | 10000+ | Human |
| α$_{2A}$ | 1114 | Human |
| α$_{2C}$ | 1540 | Human |
| β$_1$ | 10000+ | Human |
| β$_2$ | 10000+ | Human |
| β$_3$ | 10000+ | Human |
| D$_1$ | 10000+ | Human |
| D$_2$ | 3.0 | Human |
| D$_3$ | 3.5 | Rat |
| D$_4$ | 2369 | Human |
| D$_5$ | 10000+ | Human |
| H$_1$ | 10000+ | Human |
| H$_2$ | 10000+ | Human |
| H$_4$ | 10000+ | Human |
| M$_1$ | 10000+ | Human |
| M$_2$ | 10000+ | Human |
| M$_3$ | 10000+ | Human |
| M$_4$ | 10000+ | Human |
| M$_5$ | 10000+ | Human |
| σ$_1$ | 10000+ | Rat |
| σ$_2$ | 10000+ | Rat |
| MORTooltip μ-Opioid receptor | 10000+ | Human |
| DORTooltip δ-Opioid receptor | 10000+ | Human |
| KORTooltip κ-Opioid receptor | 10000+ | Human |
| GHB$^{High}$Tooltip High-affinity γ-hydroxybutyric acid receptor | 50 (IC$_{50}$Tooltip Half-maximal inhibitory concentration) | Rat |
| NMDA (PCP) | 10000+ | Rat |
| Values are K$_i$ (nM). The smaller the value, the more strongly the drug binds to the site. ||||
Amisulpride functions primarily as a dopamine D$_2$ and D$_3$ receptor antagonist. It has high affinity for these receptors with dissociation constants of 3.0 and 3.5 nM, respectively. Although standard doses used to treat psychosis inhibit dopaminergic neurotransmission, low doses preferentially block inhibitory presynaptic autoreceptors. This results in a facilitation of dopamine activity, and for this reason, low-dose amisulpride has also been used to treat dysthymia.
Amisulpride and its relatives sulpiride, levosulpiride, and sultopride have been shown to bind to the high-affinity GHB receptor at concentrations that are therapeutically relevant (IC$_{50}$Tooltip Half-maximal inhibitory concentration = 50 nM for amisulpride).
Amisulpride, sultopride and sulpiride respectively present decreasing in vitro affinities for the D$_2$ receptor (IC$_{50}$ = 27, 120 and 181 nM) and the D$_3$ receptor (IC$_{50}$ = 3.6, 4.8 and 17.5 nM).
Though it was long widely assumed that dopaminergic modulation is solely responsible for the respective antidepressant and antipsychotic properties of amisulpride, it was subsequently found that the drug also acts as a potent antagonist of the serotonin 5-HT$_7$ receptor (K$_i$ = 11.5 nM). Several of the other atypical antipsychotics such as risperidone and ziprasidone are potent antagonists at the 5-HT$_7$ receptor as well, and selective antagonists of the receptor show antidepressant properties themselves. To characterize the role of the 5-HT$_7$ receptor in the antidepressant effects of amisulpride, a study prepared 5-HT$_7$ receptor knockout mice. The study found that in two widely used rodent models of depression, the tail suspension test, and the forced swim test, those mice did not exhibit an antidepressant response upon treatment with amisulpride. These results suggest that 5-HT$_7$ receptor antagonism mediates the antidepressant effects of amisulpride.
Amisulpride also appears to bind with high affinity to the serotonin 5-HT$_{2B}$ receptor (K$_i$ = 13 nM), where it acts as an antagonist. The clinical implications of this, if any, are unclear. In any case, there is no evidence that this action mediates any of the therapeutic effects of amisulpride.
Amisulpride shows stereoselectivity in its actions. Aramisulpride ((R)-amisulpride) has higher affinity for the 5-HT$_7$ receptor (K$_i$ = 47 nM vs. 1,900 nM) while esamisulpride ((S)-amisulpride) has higher affinity for the D$_2$ receptor (4.0 nM vs. 140 nM).
Through a high direct unmetabolized excretion, it has, despite its high usual dose, also high affinity for dopamine-D$_2$-D$_3$-receptors. Also the available literature gives us hints about also relatively high receptor dissociation kinetics (through a delayed but high occupancy at dopamine receptors after 6 hours from a 100 mg exposure). Not just is this level of occupation (90%) enough for the normally therapeutic adwished level of the needing receptors occupated against schizophrenia, but even with this occuring after a single dose of amisulprid (compared with the receptoroccupation of about 12% in the striatalregion of the brain when taken cariprazine (which reaches an occupation between 63-69% not until several weeks and doses of administration)). So one can say that the dynamics of dopamin-receptoroccupation and how this does affect the human body are very complex, for example can the body and the brain work totally accurately even when over 90% of the dopaminreceptors are occupated, yet though does the triggering of presynaptic autoreceptors to enhance mood in cases of dysthymia depending on an insaturated occupation of postsynaptic D2 receptors. However, this dopamine exposure could be slightly more "balanced" providing some little advantages over haloperidol in using it for drug exposure. Due to its lack of compensatory serotonin effects and also not having an anticholinergic profile, it may not considered as an effective alternative if akathasia is a problem.

### Pharmacokinetics

The oral bioavailability of amisulpride is 48%. Its plasma protein binding is 16%. The drug is metabolized by the liver but its metabolism is minimal. Its elimination half-life is 12 hours. Amisulpride is eliminated in urine (23–46%) and feces and is excreted mostly unchanged.

## Chemistry

Amisulpride is a benzamide derivative. It is structurally related to other benzamide dopamine receptor antagonists employed as antipsychotics and antiemetics including levosulpiride, metoclopramide, nemonapride, remoxipride, sulpiride, sultopride, tiapride, and veralipride. Chemically, it is also known as aminosultopride, differing from sultopride only in possessing an amino substituent on its benzene ring.

## History

Amisulpride was introduced by Sanofi-Aventis in the 1990s. Its patent expired by 2008, and generic formulations became available.

### United States clinical development

The U.S. Food and Drug Administration (FDA) approved a 10 mg/4mL amisulpride IV formulation for use in post-operative nausea based on evidence from four clinical trials of 2323 subjects undergoing surgery or experiencing nausea and vomiting after the surgery. The trials were conducted at 80 sites in the United States, Canada and Europe.
Two trials (Trials 1 and 2) enrolled subjects scheduled to have surgery. Subjects were randomly assigned to receive either amisulpride or a placebo drug at the beginning of general anesthesia. In Trial 1, subjects received amisulpride or placebo alone, and in Trial 2, they received amisulpride or placebo in combination with one medication approved for prevention of nausea and vomiting. Neither the subjects nor the health care providers knew which treatment was being given until after the trial was complete.
The trials counted the number of subjects who had no vomiting and did not use additional medications for nausea or vomiting in the first day (24 hours) after the surgery. The results then compared amisulpride to placebo.
The other two trials (Trials 3 and 4) enrolled subjects who were experiencing nausea and vomiting after surgery. In Trial 3, subjects did not receive any medication to prevent nausea and vomiting before surgery and in Trial 4 they received the medication, but the treatment did not work. In both trials, subjects were randomly assigned to receive either amisulpride or placebo. Neither the subjects nor the health care providers knew which treatment was being given until after the trial was complete.
The trials counted the number of subjects who had no vomiting and did not use additional medications for nausea or vomiting in the first day (24 hours) after the treatment. The trial compared amisulpride to placebo.
The FDA has not approved amisulpride for use in any psychiatric indication. LB Pharmaceuticals is developing N-methyl amisulpride for the use in the treatment of schizophrenia; a Phase 2 first-in-patient study is planned for 2023.

## Society and culture
### Brand names

Brand names include: Amazeo, Amipride (AU), Amival, Deniban, Solian (AU, IE, RU, UK, ZA), Soltus, Sulpitac (IN), Sulprix (AU), Midora (RO) and Socian (BR).

### Availability

Amisulpride is not approved by the Food and Drug Administration for use in the United States in psychiatric indications, but it is approved and in use throughout Europe, Asia, Mexico, New Zealand and Australia to treat psychosis and schizophrenia.
An IV formulation of Amisulpride was approved for the treatment of postoperative nausea and vomiting ("PONV") in the United States in February 2020.

## Research
### Bipolar depression

SEP-4199 (non-racemic amisulpride), an 85:15 ratio of aramisulpride ((R)-amisulpride) to esamisulpride ((S)-amisulpride), which is theorized to provide more balanced serotonin 5-HT$_7$ and dopamine D$_2$ receptor antagonism than racemic amisulpride (a 50:50 ratio of its (R)- and (S)-enantiomers), is or was under development by Sunovion Pharmaceuticals for the treatment of bipolar depression in the United States and other countries. However, its development may have been discontinued.

### Chemotherapy-induced nausea and vomiting

The intravenous formulation of amisulpride approved for treatment of postoperative nausea and vomiting is additionally under development for the treatment of chemotherapy-induced nausea and vomiting.

### Chemical derivatives

A more lipophilic and centrally permeable derivative of amisulpride, N-methylamisulpride (developmental code name LB-102), is under development by LB Pharmaceuticals for the treatment of schizophrenia in the United States and other countries.