Neuroleptic malignant syndrome is a life-threatening adverse reaction to certain anti-psychotic and neuroleptic pharmaceuticals. It is characterized by muscle rigidity, fever, instability of autonomic functions such as heart rate and respiration, and delirium. It is often accompanied with elevated creatine phosphokinase levels.
The condition is rare to begin with and is getting less common as dosage controls for these medications are adjusted. The symptoms are slow to onset, taking about three days to fully develop. However, once the condition is established, it can last any period of time from less than a day to six weeks. The condition is difficult to diagnose. It is usually first seen as an onset of the patient's regular mental illness. It is often also mistaken for encephalitis and heat stroke.
Treatment is entirely supportive. It usually starts with rapidly cooling the fever, discontinuing the drug and supporting kidney function with hydration and diuresis. The prognosis improves the earlier treatment starts and the more aggressive it is. Common complications are hypertensive crisis and acidosis.