Amisulpride

Amisulpride (sold as Solian, Sulpitac, Amitrex or Soltus), is an atypical antipsychotic used to treat psychosis in schizophrenia and episodes of mania in bipolar disorder. In small doses it is also used to treat depression. It was introduced by Sanofi-Aventis in the 1990s.

Pharmacology

Amisulpride functions primarily as a D₂ and D₃ receptor antagonist. It has high affinity for these receptors with dissociation constants of 2.8 nM and 3.2 nM, respectively. Although standard doses in the 400 to 1200 mg a day range used to treat psychosis inhibit dopaminergic neurotransmission, low doses in the 50 to 200 mg range preferentially block inhibitory pre-synaptic autoreceptors. This results in a facilitation of dopamine activity, and for this reason, low dose amisulpride has also been used to treat clinical depression.

Amisulpride and its relative sulpiride have been shown to bind to and activate the GHB receptor at doses that are used for therapeutic purposes.^[3] Activation of the GHB receptor is known to inhibit the release of dopamine and even appears to have neuroleptic effects itself . For this reason it is believed that amisulpride and sulpiride's action at this receptor may contribute to their efficacy in treating psychosis.

Though it has long been widely assumed that dopaminergic modulation is solely responsible for the respective antidepressant and antipsychotic properties of amisulpride, it has recently been shown that it also acts as a potent antagonist at the 5-HT₇ receptor.^[4] Several of the other atypical antipsychotics such as risperidone and ziprasidone are potent antagonists at the 5-HT₇ receptor as well, and selective antagonists of the receptor show antidepressant properties themselves. To characterize the role of the 5-HT₇ receptor in the antidepressant effects of amisulpride, a study prepared 5-HT₇ receptor knockout mice.^[4] 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.^[4] These results indicate that 5-HT₇ receptor antagonism plays a major role in the antidepressant effects of amisulpride.^[4]

Availability

Amisulpride is not approved by the Food and Drug Administration for use in the United States, but it is used in Europe (France, Germany, Italy, Switzerland, Russia, United Kingdom, etc.) and Australia to treat psychoses and schizophrenia.^[5][6] In Italy, in 50 mg doses, it is also used as a treatment for dysthymia (under the brand name Deniban).

Efficacy as an antidepressant

As an antidepressant, amisulpride is significantly more effective than :

• Sertraline (Zoloft)^[7]
• Imipramine (Tofranil)^[8]

and equal to :

• Amitriptyline (Elavil, Endep)^[9]
• Amineptine^[10]

In another study, anxiety measured by HAM-A total mean score decreased significantly more with amisulpride 50 mg/day (63%) than with fluoxetine (Prozac)20 mg/day (54%; P = 0.021).^[11] Another recent study^[12] concludes that amisulpride is an appropriate first-line treatment for the management of acute psychosis.

Side effects

Prolactin induction, thereby causing amenorrhoea and galactorrhoea in women, nausea, weight gain, insomnia, akathisia, sexual dysfunction, although much less than similar drugs in its class, and less commonly QT interval prolongation (which can lead to serious heart arrhythmias). Overdoses of amisulpride have been linked with torsades de pointes.^[13]

See also

Tardive dyskinesia, reported as possible side effect

References