CNS Part- 2
In comparing neuroleptics, which of the following is most likely associated with skeletal muscle rigidity, tremor at rest, flat facies uncontrollable restlessness, and spastic torticollis? (AIPG 2009)
a. Haloperidol is the most potent typical antipsychotic drugs. Haloperidol, a butyrophenone is by far the most likely antipsychotic to cause extrapyramidal responses. Other agents, such as piperazine (an aromatic phenothiazine), thiothixene (a thioxanthene), or pimozide (a diphenylbutyropiperidine less likely to produce extrapyramidal toxicity than haloperidol.
b. The antagonism of dopamine in the nigrostriatal system might explain the Parkinson-like effects. Both haloperidol and pimozide act mainly on D2 receptors, whereas thiothixene and piperazine act on α-adrenergic receptors, and have a less potent but definite effect on D2 receptors.