Amisulpride

Amisulpride is a substituted benzamide, a chemical family that also includes the older antipsychotic sulpiride and the antiemetic metoclopramide. It is classed among the atypical antipsychotics, drugs that treat psychosis with a lower tendency to cause movement side effects than the older agents. Unlike many atypicals, which act broadly across dopamine and serotonin receptors, amisulpride is a comparatively selective antagonist of dopamine D2 and D3 receptors ^[1].

A distinctive feature of amisulpride is that its effects depend on dose. At higher doses it blocks postsynaptic D2 and D3 receptors, producing an antipsychotic effect suited to the positive symptoms of schizophrenia, whereas at low doses it preferentially blocks presynaptic autoreceptors, which increases dopamine release and is used to treat negative symptoms and depressed mood ^[1]. Research has also shown that amisulpride is a potent antagonist of the serotonin 5-HT7 receptor, an action that appears to underlie its antidepressant properties independently of its dopamine effects ^[1].

In schizophrenia, comparative studies place amisulpride among the more effective antipsychotics. A large network meta-analysis of many antipsychotic drugs ranked it near the top for efficacy and found it had one of the lowest rates of patients stopping treatment, though it was also among those more likely to raise the hormone prolactin ^[3]. A systematic review comparing it with other second-generation drugs found similar efficacy to olanzapine and risperidone, with less weight gain ^[2]. Separately, low-dose intravenous amisulpride has been shown in randomized trials to reduce postoperative nausea and vomiting after surgery, leading to approval of an injectable form for that use ^[4].

Oral amisulpride is widely used for schizophrenia in Europe, Australia, and many parts of Asia, but it has never been approved for psychiatric indications in the United States. The intravenous formulation for postoperative nausea and vomiting, however, was approved by United States regulators, giving the drug a distinct regulatory status across its two very different uses ^[4].

Amisulpride is only modestly absorbed after oral dosing, binds weakly to plasma proteins, and is eliminated largely unchanged by the kidneys. It penetrates the brain relatively poorly, a feature linked to its strong effect on prolactin, since the pituitary gland lies largely outside the blood-brain barrier ^[1]. It is available as oral tablets and, for the antiemetic indication, as a solution for intravenous injection.

Even at low doses it can raise prolactin (the milk hormone), which can mean breast tenderness, cycle changes, or lowered libido; that is its most reliable nuisance. Higher doses carry the antipsychotic risks: movement side effects and, rarely, QT prolongation (a heart rhythm issue), so it is dose and heart dependent. It is renally cleared, so kidney function matters. Prescription drug, not sold in the US.

Amisulpride prolongs the QT interval in a dose and concentration dependent way, and that is the interaction that matters most. Taken with other QT prolonging agents, such as class Ia and class III antiarrhythmics, droperidol, methadone or other antipsychotics, the risk of torsades de pointes rises; the same applies to anything that depletes potassium or magnesium, since low electrolytes lower the threshold for arrhythmia.

As a selective dopamine D2 and D3 antagonist, amisulpride works directly against levodopa and dopamine agonists. Each blunts the other, so motor control worsens on one side while antipsychotic effect is lost on the other.

Metabolic interactions are unusually few. Amisulpride is barely touched by cytochrome P450 enzymes and leaves the body largely unchanged in urine, so CYP inhibitors and inducers do little to it. What does raise exposure is reduced kidney function, whether from disease or from a nephrotoxic co-medication. Additive sedation with alcohol, benzodiazepines and opioids is also documented.

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Amisulpride is a benzamide-class antipsychotic developed by the French company Synthelabo and derived from the earlier drug sulpiride. It was introduced in Europe in the 1990s under the trade name Solian and became a widely used treatment for schizophrenia, with low doses employed in some countries for depressive conditions such as dysthymia. Although it has never been approved as an antipsychotic in the United States, a distinct low-dose intravenous formulation was approved by the United States Food and Drug Administration in 2020 for the prevention and treatment of postoperative nausea and vomiting. Its selective, dose-dependent action on dopamine receptors has made it a subject of continued pharmacological interest.

Amisulpride has earned a strong reputation for efficacy, ranking among the most effective antipsychotics in large network meta-analyses of schizophrenia treatment, including landmark Lancet comparisons of 15 and later 32 agents. Clinicians particularly note its effectiveness against negative symptoms at lower doses and its relatively favorable movement-side-effect profile, attributed to its preference for limbic over motor dopamine pathways. Its antagonism of the serotonin 5-HT7 receptor is thought to underlie antidepressant effects that distinguish it from many peers. Balanced against these strengths are well-known cautions, chiefly its tendency to raise prolactin levels and to prolong the cardiac QT interval, which call for appropriate monitoring.