Perospirone

Perospirone is a serotonin 5-HT2 receptor inverse agonist and dopamine D2 receptor antagonist based on receptor binding experiments that binds to both receptors with high affinity. Perospirone is also a partial agonist at 5-HT1A receptors which are autoreceptors that stimulate the uptake of 5-HT and inhibit 5-HT release. It also interacts with D4 receptors and α₁-adrenergic receptors as an antagonist, as well as histamine H1 receptor an inverse agonist. Binding to these receptors may explain sedative and hypotensive actions. Perospirone binds to D1 receptors with low affinity and minimal clinical significance.

Antagonism at D2 receptors is believed to relieve the positive symptoms of schizophrenia such as delusions, hallucinations, and thought disorders. Perospirone targets the mesolimbic patway to reverse the overactivity of the dopaminergic signalling via D2 receptors. 5-HT2A antagonism is thought to allevaite the negative symptoms and cognitive impairments of schizophrenia. These receptors are Gi/Go coupled receptors that lead to decreased neurotransmitter release and neuronal inhibition when activated, thus play a role in dopamine release regulation. Perospirone targets these receptors in the nigrostriatal pathway to reduce dopamine release and function. In contrast, 5-HT2A receptor antagonism may improve the negative symptoms by enhancing dopamine and glutamate release in the mesocortical pathway. 5-HT1A receptor activation further inhibits the release of 5-HT into the synaptic cleft.

Perospirone undergoes rapid and extensive first-pass metabolism in the liver; the metabolic pathways involve hydroxylation, N-dealkylation, and S-oxidation, which are catalyzed by CYP1A1, 2C8, 2D6, and 3A4. CYP3A4 is reported to have highest level of contribution in perospirone metabolism. Hydroxyperospirone is formed from hydroxylation of the the cyclohexane-1,2-dicarboximide moiety and retains pharmacological action by mediating antiserotonergic effects, although with lower affinity.

Perospirone has known human metabolites that include 3-(1-Piperazinyl)-1,2-benzisothiazole, (3aS,7aR)-2-(4-hydroxybutyl)-3a,4,5,6,7,7a-hexahydroisoindole-1,3-dione, (3aS,7aR)-2-[4-[4-(1,2-benzothiazol-3-yl)piperazin-1-yl]butyl]-5-hydroxy-3a,4,5,6,7,7a-hexahydroisoindole-1,3-dione, 4,5,6,7-Tetrahydro-2-[4-[4-(1,2-benzisothiazole-3-yl)piperazino]butyl]-2H-isoindole-1,3-dione, and (3As,7aS)-2-[4-[4-(1,2-benzothiazol-3-yl)piperazin-1-yl]butyl]-7a-hydroxy-4,5,6,7-tetrahydro-3aH-isoindole-1,3-dione.

Agents that control agitated psychotic behavior, alleviate acute psychotic states, reduce psychotic symptoms, and exert a quieting effect. They are used in SCHIZOPHRENIA; senile dementia; transient psychosis following surgery; or MYOCARDIAL INFARCTION; etc. These drugs are often referred to as neuroleptics alluding to the tendency to produce neurological side effects, but not all antipsychotics are likely to produce such effects. Many of these drugs may also be effective against nausea, emesis, and pruritus.

Perospirone is rapidly absorbed following oral administration with the time to reach peak plasma concentration of 0.8 to 1.5 hours. A single oral dose of 8mg perospirone results in peak plasma concentration of 5.7 ug/L. Perospirone is not reported to be accumulated after repeated dosing.

Perospirone is mainly excreted via renal elimination. 0.4% of of total dose is excreted as unchanged drug following oral administration of 8mg perospirone.

The mean volume of distribution following oral administration of 32 mg/day of perospirone is 1733L, with values ranging from 356-5246 L. It is shown to cross the placenta and be secreted into milk in pregnant rats.

Apparent clearance rate is approximately 425.5 ± 150.3 L/h in patients receiving a single oral dose of 8mg perospirone.