Neuroleptic malignant syndrome: a case-based approach

The presentation

Imagine an adult who has recently started, or had an increase in, a medicine for a mental health condition. Over a day or two they become very stiff and rigid in the muscles, develop a high temperature, and seem confused, drowsy or less responsive than usual. They may be sweating heavily, have an unstable heartbeat and blood pressure, and appear generally very unwell. Family might notice they move stiffly, seem "locked up", or are difficult to rouse. This combination — high temperature, marked muscle stiffness, confusion and signs that the body's automatic controls are disturbed, coming on after starting or increasing an antipsychotic-type medicine — is the hallmark of neuroleptic malignant syndrome. It builds up over hours to days and is quite different from a simple side effect, which is why it needs urgent recognition.

Why it is dangerous

Medicines that block dopamine can, in rare cases, disturb the body's control of temperature and muscle activity. In neuroleptic malignant syndrome the muscles become rigid and overactive, generating heat and driving the temperature up, while the systems that regulate heart rate and blood pressure become unstable. The intense muscle activity can cause muscle tissue to break down, releasing substances that can harm the kidneys, and the high temperature and instability put the whole body under severe strain. If not treated promptly, it can affect breathing, the kidneys and other organs and can be life-threatening. This is why, although the reaction is rare, it is treated as a serious emergency: the affected medicine must be stopped and the person supported in hospital, where the temperature, fluids and other problems can be managed closely.

When to call 999

Call 999 or go straight to A&E if someone taking an antipsychotic or similar dopamine-blocking medicine develops a high temperature together with stiff or rigid muscles, confusion or reduced consciousness, heavy sweating, or a fast or unstable heartbeat. These features together are a medical emergency. It is important to tell the emergency team exactly which medicines the person takes and about any recent change in dose or a newly started medicine, as this is a vital clue to the diagnosis. Do not delay to see whether the temperature settles. While waiting for help, keep the person cool and calm, encourage fluids if they are alert enough to drink safely, and gather their medicines or a medication list so the team can see everything they are taking.

Who is more at risk

Neuroleptic malignant syndrome is most associated with antipsychotic medicines used for conditions such as schizophrenia and bipolar disorder, but it can also occur with some other dopamine-blocking medicines, including certain treatments for nausea. The risk is thought to be higher soon after starting one of these medicines, after a dose increase, or when switching or combining them. Being dehydrated, physically unwell or agitated may add to the risk in some people. It can also occur, in a similar form, when medicines used for Parkinson's disease are stopped suddenly, because these boost dopamine. Because a recent medicine change is often the trigger, anyone starting or altering such medicines should be aware of the warning features, and carers should know to seek urgent help if they appear.

The safe pathway

The practical rule is to treat the combination of high temperature and muscle stiffness in someone on these medicines as an emergency. If a person taking an antipsychotic or similar medicine becomes hot, rigid, confused and very unwell, call 999 or go to A&E and make clear which medicines they take and what has changed recently. In hospital the responsible medicine is stopped and the person is cooled, given fluids and supported while they recover, with close monitoring of the temperature, muscles and kidneys. To reduce risk, medicines of this kind should be started, changed and stopped only with medical guidance, and Parkinson's medicines should never be stopped suddenly without advice. Neuroleptic malignant syndrome is rare, but because it is serious and comes on over hours to days, early recognition and prompt hospital care are what keep people safe.