Neuroleptic malignant syndrome

Neuroleptic malignant syndrome
Haloperidol, a known cause of NMS
Specialty	Critical care medicine, neurology, psychiatry
Symptoms	High fever, confusion, rigid muscles, variable blood pressure, sweating[1]
Complications	Rhabdomyolysis, high blood potassium, kidney failure, seizures[1][2]
Usual onset	Within a few weeks or days[3]
Causes	Antipsychotic medication[1]
Risk factors	Dehydration, agitation, catatonia[4]
Diagnostic method	Based on symptoms in someone who has started on antipsychotics within the last month[2]
Differential diagnosis	Heat stroke, malignant hyperthermia, serotonin syndrome, lethal catatonia[2]
Treatment	Stopping the offending medication, rapid cooling, starting other medications[2]
Medication	Dantrolene, bromocriptine, diazepam[2]
Prognosis	10–15% risk of death[4]
Frequency	15 per 100,000 per year (on neuroleptics)[1]

Neuroleptic malignant syndrome (NMS) is a rare^[5][6] but life-threatening reaction that can occur in response to antipsychotics (neuroleptic) or other drugs that block the effects of dopamine.^[1][7] Symptoms include high fever, confusion, rigid muscles, variable blood pressure, sweating, and fast heart rate.^[1] Complications may include muscle breakdown (rhabdomyolysis), high blood potassium, kidney failure, or seizures.^[1][2]

Any medications within the family of antipsychotics can cause the condition, though typical antipsychotics appear to have a higher risk than atypicals,^[1] specifically first generation antipsychotics like haloperidol.^[5] Onset is often within a few weeks of starting the medication but can occur at any time.^[1][3] Risk factors include dehydration, agitation, and catatonia.^[4]

Rapidly decreasing the use of levodopa or other dopamine agonists, such as pramipexole, may also trigger the condition.^[1][8] The underlying mechanism involves blockage of dopamine receptors.^[1] Diagnosis is based on symptoms.^[2]

Management includes stopping the triggering medication, rapid cooling, and starting other medications.^[2] Medications used include dantrolene, bromocriptine, and diazepam.^[2] The risk of death among those affected is about 10%.^[4] Rapid diagnosis and treatment is required to improve outcomes.^[1] Many people can eventually be restarted on a lower dose of antipsychotic.^[2][3]

As of 2011, among those in psychiatric hospitals on antipsychotics about 15 per 100,000 are affected per year (0.015%).^[1] In the second half of the 20th century rates were over 100 times higher at about 2% (2,000 per 100,000).^[1] Males appear to be more often affected than females.^[1] The condition was first described in 1956.^[1]