Neuroleptic malignant syndrome is a rare but potentially life threatening idiosyncratic complication of neuroleptic drugs. Levenson criteria do help guide in diagnosis of NMS and the major manifestations of the syndrome are muscular rigidity, fever, autonomic dysfunction and altered consciousness. NMS mortality is approximately between 10 to 20%.

The authors present and discuss the case of a patient with mental retardation who developed neuroleptic malignant syndrome after receiving haloperidol and zuclopenthixol for agitation.

Supportive therapy including rehydratation, electrolyte restoration, paracetamol, dantrolene and biperideno were given to the patient.

Supportive therapy, dantrolene and biperideno yielded clinical benefits for neuroleptic malignant syndrome. However the patient developed acute hepatic failure probably secondary to dantrolene with need of admission to an intensive gastroenterological care unit, where he stayed for approximately one month.

Although neuroleptic malignant syndrome and acute liver failure due to dantrolene are rare emergencies, the patient presented in this case developed theses two idiosyncratic, rare and potentially fatal reactions due to haloperidol, zuclopenthixol and dantrolene administration. This report clearly represents a successful clinical outcome only possible due to an early diagnosis and prompt treatment interventions.