Malignant neuroleptic syndrome is caused by: March 2009

Ans. C: Antipsychotics Neuroleptic malignant syndrome (NMS) refers to the combination of hypehermia, rigidity, and autonomic dysregulation that can occur as a serious complication of the use of antipsychotic drugs. The list of atypical antipsychotic drugs that may cause NMS include olanzapine, risperidone, paliperidone, aripiprazole, ziprasidone, amisulpride, and quetiapine. Clozapine may also be associated with the development of NMS, but it appears to be less likely to manifest with extrapyramidal features, including rigidity and tremor. The most widely accepted mechanism by which antipsychotics cause neuroleptic malignant syndrome is that of dopamine D2 receptor antagonism. Central D2 receptor blockade in the hypothalamus, nigrostriatal pathways, and spinal cord leads to increased muscle rigidity and tremor extrapyramidal pathways. Hypothalamic D2 receptor blockade results in an elevated temperature set point and impairment of heat-dissipating mechanisms. Peripherally, antipsychotics lead to increased calcium release from the sarcoplasmic reticulum, resulting in increased contractility, which can contribute to hypehermia, rigidity, and muscle cell breakdown.