Antagonist thioxanthenes

The differential clinical actions of DA blockers on the DA receptor subtypes have not been defined with precision. Most neuroleptics appear to act at both D-1 and D-2 receptors. Some differences exist, however. The thioxanthenes bind to sites related to both DA receptor subtypes, but the butyrophenones seem to prefer sites assocaited with D-2 receptors, binding only weakly to those identified with D-1 receptors. Sulpiride, molindone and metoclopramide are relatively selective D-2 antagonists. 

Conventional antipsychotic (neuroleptic, thioxanthene, dopamine 2 antagonist)... 

Dopamine-receptor antagonists having antipsychotic properties, such as phenothiazine, butyrophenone, and thioxanthene derivatives, and Gl-stimulant drugs, such as metoclopramide, are contraindicated with pergolide. The... 

Phenothiazines, butyrophenones, diphenylbutylpiperidines and thioxanthenes can oppose the effects of levodopa because of their dopamine antagonist properties, causing deterioration of motor function in Parkinson s disease. The antipsychotic effects and ex-trapyramidal adverse effects of these drugs can be opposed by levodopa. Of the atypical antipsychotics, risperidone and olanzapine cause deterioration in motor function in Parkinson s disease. Ziprasidone may act similarly, and there have been reports with quetiapine. Clozapine does not have this effect. 

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