Antipsychotics interact with a number of receptors, including dopamine receptors, the receptor system involved in psychosis, which is theorized to occur as a result of a functional excess of dopamine in certain parts of the brain. Many antipsychotics work by targeting dopamine receptors, such that dopamine levels are reduced. Antagonism of the dopamine D2 receptor subtype, is one well characterized mechanism of action, although other receptors, including non-dopamine receptors, are involved, depending on the antipsychotic.
The older antipsychotics are also known as "typical antipsychotics" or "first generation antipsychotics". More recently developed antipyschotics are also known as "atypical antipsychotics" or "second generation antipsychotics". The atypical or second generation antipsychotics are also active at other receptors, including serotonin receptors, such that side effects, especially motor ones, are thought to be reduced. Neuroleptics is another commonly used name, although its use has fallen out of favor.
Well known antipsychotics include haloperidol (Haldol) and chlorpromazine (Thorazine), which are older agents. The newer agents, many developed near the 1990's, include risperidone (Risperdal), olanzapine (Zyprexa), quetiapine (Seroquel), and aripiprazole (Abilify). Aripiprazole is thought to be a dopamine system stabilizer in that it acts as a funtional antagonist of dopamine where dopamine levels are in excess and a functional agonist where dopamine levels are low.