At low doses, specifically binds to presynaptic D2 receptors, enhancing dopamine transmission and believed to be the mechanism for improving negative symptoms. At high doses, it blocks postsynaptic dopamine receptors. At low doses sulpiride can improve apathy associated with negative symptoms. At high doses, it is used to improve the florid positive symptoms of schizophrenia. Sulpiride acts on D4 and D5 receptors at low doses and at high doses, it blocks D2 receptors.
Side effects are as in Chlorpromazine but less common than chlorpromazine.
Zotepine has been around for several years for treating both positive and negative symptoms of schizophrenia in Germany and Japan but first became available in the UK in 1998. The drug has a lower incidence of EPS than typical drugs but it can increase prolactin levels and like olanzapine, it is associated with weight gain. Zotepine acts primarily on 5HT2 receptors and also on D2 and a, 2c, receptors and , D1 and D3 and D4 is a noradrenaline reuptake inhibitor. The first antipsychotic drug used for schizophrenia, chlorpromazine was introduced in 1952. A member of the phenothiazine group of neuroleptics, it is now used for a range of psychotic conditions including schizophrenia.