Conditions and symptoms
What Is Neuroleptic Malignant Syndrome? Signs to Know
Neuroleptic malignant syndrome · say it: noo-roh-LEP-tik muh-LIG-nunt SIN-dromeAlso written: NMS
Short answer
Neuroleptic malignant syndrome is a rare, serious reaction to antipsychotics and some other medicines, with fever, stiff muscles and confusion. It is urgent.
What it means
Neuroleptic malignant syndrome (NMS) is a rare but life-threatening reaction, most often linked to antipsychotic medicines, and sometimes to anti-sickness medicines or to suddenly stopping Parkinson's medicines. Signs include high fever, very stiff muscles, confusion or reduced alertness, sweating, and changes in heart rate or blood pressure. It is an emergency: anyone with these signs needs urgent medical help straight away.
Antipsychotic labels list NMS so that it is recognised early. It most often develops in the first weeks of treatment or after a dose increase, but can happen at other times. The warning is telling you and your family to seek urgent help if fever and muscle stiffness appear together, rather than treating it as a simple infection at home.
'Malignant' here means dangerous, not cancer. NMS is often compared with serotonin syndrome, which is caused by too much serotonin activity and tends to come on faster, with twitching and shivering rather than rigid stiffness.
Where you may see it
- The 'Warnings' section of antipsychotic labels
- Metoclopramide and some anti-sickness medicine labels
- Hospital and psychiatry records
📄 How it looks on a report
Neuroleptic Malignant Syndrome, a potentially fatal symptom complex, has been reported in association with administration of antipsychotic drugs.
🙅 What it does not mean
- 'Malignant' does not mean cancer.
- It is rare; being on the label does not mean it will happen to you.
- Fever alone does not mean NMS, but fever with stiff muscles and confusion needs urgent help.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “Neuroleptic malignant syndrome”
Plain-English explanations of each medicine, from its official FDA label.
- Aripiprazole
an atypical antipsychotic medicine
- Metoclopramide
A stomach and gut medicine. The label describes it as affecting how the stomach and intestines move. The label does not give an FDA drug class.
- Risperidone
an atypical antipsychotic medicine
🔗 Read more from trusted sources
- “Neuroleptic malignant syndrome” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “neuroleptic malignant syndrome”
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