Neuroleptic malignant syndrome (NMS)

What is Neuroleptic Malignant Syndrome (NMS)?

Neuroleptic Malignant Syndrome is a very rare, but serious and life-threatening condition triggered by an allergic reaction to medications known as neuroleptics, which are taken primarily to treat mental health disorders such as schizophrenia, bipolar disorder, and depression.

It is a medical emergency that requires hospitalization and close monitoring. Symptoms can include fever, rigidity, tremors, confusion, elevated heart rate and blood pressure, and changes in levels of consciousness. NMS usually occurs between two and 14 days after neuroleptic medication is started.

Common Signs and Symptoms of NMS:

  • Fever
  • Confusion
  • Stiffness
  • Sweating
  • Rapid pulse and heart rate
  • Agitation
  • Changes in breathing
  • Seizures
  • Coma

Causes of Neuroleptic Malignant Syndrome:

NMS is most commonly associated with starting a new medicine, increasing the dose of medicine, or decreasing the dose too quickly.

Research suggests that some people may be more vulnerable to NMS than others due to genetics or underlying medical conditions. People with conditions that cause severe rigidity, such as Parkinson’s disease, may be at an increased risk.


If NMS isn't treated, it can lead to serious complications, such as rhabdomyolysis, renal failure, cardiomyopathy, cardiac arrhythmias, or respiratory failure. Rarely, NMS may even be fatal.

Treatment of Neuroleptic Malignant Syndrome:

NMS is a medical emergency that requires immediate hospitalization. During treatment, the person is closely monitored for vital signs such as heart rate, blood pressure, and temperature.

Medications such as dantrolene (Dantrium) or bromocriptine (Parlodel) can be prescribed to reduce muscle rigidity, while benzodiazepines and antipyretics can also be used to address other symptoms. The person may also be given fluids and electrolytes through an IV to help restore normal body functions.

The person's medications must also be stopped, and they may need to be given antipsychotics or other drugs to address any psychiatric symptoms.

Prevention of NMS:

There are specific things you can do to reduce your risk of developing NMS:

  • Talk to your doctor about any underlying medical conditions that may increase your risk of developing NMS.
  • Be aware of the signs and symptoms of NMS and seek medical help if you experience any of them after starting a new medication.
  • Follow your doctor's directions carefully when taking any medications, including instructions on dose and frequency.
  • Ask your doctor about any potential side effects of your medications, including NMS.


NMS is a rare but serious condition that can be fatal if not treated promptly. It is most commonly associated with neuroleptics, but can occur with other medications as well. Being aware of the signs and symptoms and taking steps to prevent NMS can help reduce your risk.