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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Neuroleptic malignant syndrome

Neurology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Time-critical presentation

Neuroleptic malignant syndrome is a medical emergency. Stop dopamine antagonists, call critical care and toxicology, begin active cooling and supportive resuscitation, and monitor for rhabdomyolysis, hyperkalaemia, acute kidney injury, arrhythmia, aspiration and disseminated intravascular coagulation. Severe rigidity, hyperthermia, reduced consciousness or autonomic instability requires high-dependency or intensive-care management.

Overview

Recognise dopamine-related hyperthermic rigidity, stop the precipitant, prevent renal and cardiorespiratory injury, and distinguish neuroleptic malignant syndrome from serotonin toxicity, catatonia, infection and seizures.

NMS is a clinical syndrome of impaired central dopaminergic activity and intense muscle metabolism. It can follow initiation or escalation of an antipsychotic, antiemetic dopamine antagonist or another dopamine-blocking drug. Abrupt cessation of levodopa or dopamine agonists can produce a clinically similar parkinsonism-hyperpyrexia syndrome. Medication reconciliation must include depot injections, peri-operative antiemetics and recent omissions as well as tablets listed on the current chart.

Differential diagnosis determines safe therapy. Serotonin syndrome usually begins rapidly after a serotonergic change and features spontaneous or inducible clonus, ocular clonus, hyperreflexia and gastrointestinal activity. Malignant catatonia often has a prodrome of agitation, psychosis, mutism, negativism or posturing before fever and instability and can occur without a dopamine blocker. Meningitis, encephalitis, sepsis, heatstroke, thyroid storm, malignant hyperthermia, anticholinergic poisoning and non-convulsive status require targeted investigation in parallel.

Aetiology

01

Dopamine-receptor blockade

Antipsychotics and other dopamine antagonists can trigger NMS, especially after initiation, rapid escalation, parenteral or depot administration.

02

Dopaminergic withdrawal

Abrupt reduction of levodopa, dopamine agonists or device-delivered dopaminergic treatment can produce a closely related hyperpyrexia and rigidity syndrome.

03

Physiological susceptibility

Agitation, dehydration, restraint, acute illness and previous NMS increase risk but are not necessary for the reaction.

Pathophysiology

  1. 1
    Central dopamine disruption

    Abrupt reduction in dopamine signalling impairs hypothalamic temperature and autonomic control and basal-ganglia regulation of muscle tone.

  2. 2
    Sustained rigidity and heat

    Generalised muscle contraction generates heat and raises metabolic demand while autonomic instability reduces effective heat dissipation.

  3. 3
    Muscle breakdown

    Prolonged contraction injures muscle fibres, releasing creatine kinase, potassium and myoglobin into the circulation during severe rigidity.

  4. 4
    Systemic organ failure

    Hyperthermia, dehydration, acidosis and rhabdomyolysis then cause kidney, cardiac, respiratory and coagulation complications during fulminant disease.

Clinical features and red flags

Medication-linked evolution

Confusion and stiffness progress over days after antipsychotic initiation, dose increase, depot injection or abrupt withdrawal of dopaminergic Parkinson treatment.

Lead-pipe rigidity

Sustained generalised resistance affects axial and limb muscles without the prominent rhythmic clonus expected in serotonin toxicity.

Autonomic instability

Labile blood pressure, tachycardia, diaphoresis, tachypnoea and urinary incontinence accompany rising temperature and mental-state change.

Rhabdomyolysis

Muscle pain, dark urine, high CK, potassium rise and kidney injury reflect sustained contraction and require urgent fluid and biochemical management.

Severe systemic injuryRed flag

Temperature rise with dysrhythmia, hypoxia, acidosis, oliguria, coagulopathy or reduced consciousness requires immediate intensive-care escalation.

Catatonic overlap

Mutism, negativism, posturing or a psychiatric prodrome before autonomic collapse raises malignant catatonia and may make benzodiazepine or ECT particularly important.

Investigations

  1. 01
    Complete medicine timelineFirst step
    Why
    Identify dopamine blockade, depot exposure, interaction or dopaminergic withdrawal.
    Interpretation and limitations
    Record exact doses and dates of antipsychotics, antiemetics, Parkinson medicines and serotonergic drugs; long-acting exposure persists after the drug is stopped.
  2. 02
    Creatine kinase and urinalysis
    Why
    Quantify muscle injury and detect myoglobinuria.
    Interpretation and limitations
    Trend rather than rely on one value; a large rise supports severity, while myoglobin on dipstick with few red cells warns of renal pigment injury.
  3. 03
    Renal profile, electrolytes and blood gas
    Why
    Detect acute kidney injury, hyperkalaemia, calcium or phosphate change and acidosis.
    Interpretation and limitations
    Life-threatening potassium or acidosis needs immediate treatment; frequent reassessment guides fluids and renal replacement discussion.
  4. 04
    Full blood count, liver tests and clotting
    Why
    Assess systemic inflammation, tissue injury and disseminated coagulation.
    Interpretation and limitations
    Leucocytosis and transaminase elevation are supportive but non-specific; falling platelets or abnormal clotting indicates severe complication.
  5. 05

Differential diagnosis

01

Serotonin syndrome

Rapid onset with clonus, hyperreflexia and gastrointestinal activation after serotonergic exposure favours serotonin toxicity over lead-pipe rigidity.

02

Malignant catatonia

A preceding psychomotor syndrome with mutism, negativism or excitement may favour malignant catatonia, though clinical overlap is substantial.

03

Sepsis or CNS infection

Fever, altered consciousness and shock require cultures and infection assessment; NMS should not become a reason to withhold antimicrobials when indicated.

04

Status epilepticus or malignant hyperthermia

Ictal EEG activity, recent anaesthetic exposure and event timing help distinguish ongoing seizures from anaesthesia-related malignant hyperthermia.

Management

01First hourStop exposure and stabilise physiologyFirst stepHyperthermia, rigidity and mental-state change follows dopamine blockade or withdrawal.+
  1. 1Stop the suspected culprit and non-essential psychoactive medicines, restore omitted dopaminergic therapy only through specialist advice and contact critical care and poisons information.
  2. 2Use ABCDE assessment, active external cooling, intravenous fluids, cardiac monitoring and rapid treatment of hypoxia, hyperkalaemia, seizure and aspiration.
  3. 3Minimise struggling and restraint, use benzodiazepine for severe agitation when safe, and record temperature, rigidity, urine output and neurological state repeatedly.
02Diagnostic separationDistinguish toxic, infective and catatonic syndromesThe hyperthermic movement syndrome remains diagnostically uncertain.+
  1. 1Examine specifically for clonus, hyperreflexia, bowel hyperactivity, dry skin, lead-pipe rigidity, posturing, meningism, focal signs and exposure history.

Complications

01

Rhabdomyolysis and acute kidney injury

Myoglobin, dehydration and shock damage kidneys and cause dangerous electrolyte disturbance during severe systemic rhabdomyolysis and collapse.

02

Arrhythmia and circulatory collapse

Autonomic instability, hyperkalaemia and acidosis can cause malignant arrhythmia, hypotension and multi-organ hypoperfusion during fulminant illness.

03

Aspiration and coagulation injury

Reduced consciousness and rigidity promote aspiration, while severe systemic inflammation may cause thrombosis or disseminated coagulation abnormalities.

04

Recurrence and psychiatric destabilisation

Re-exposure can trigger recurrence, but prolonged avoidance of necessary treatment may allow severe psychotic or mood relapse.

Monitoring and follow-up

  • Record core temperature, rigidity, mental state, heart rate, blood pressure, respiratory status and urine output frequently until clearly stable.
  • Trend CK, potassium, calcium, phosphate, creatinine, bicarbonate, liver tests and clotting, adjusting sampling to severity rather than once daily automatically.
  • Use continuous ECG monitoring during autonomic instability, electrolyte disturbance and any QT-prolonging or dopamine-restoring treatment.
  • Inspect pressure areas and swollen compartments and prevent venous thrombosis, aspiration and pressure injury during immobility.
  • Track fluid input and output while balancing rhabdomyolysis renal protection against pulmonary oedema and cardiac comorbidity.
  • After recovery document the culprit, reaction, future antipsychotic plan and patient-held warning so accidental rechallenge is less likely.

Special situations

CK is supportive

A dramatic rise strengthens the diagnosis and measures injury, but early or atypical NMS can occur before CK becomes abnormal.

Depot exposure persists

Stopping injections cannot remove medicine already released, so a long-acting antipsychotic may produce a prolonged course despite immediate recognition.

Heat is muscular

External cooling and reduction of contraction matter because paracetamol does not reset the drug-induced hypermetabolic process.

Withdrawal can mimic blockade

Abrupt levodopa or dopamine-agonist cessation can cause parkinsonism-hyperpyrexia with a nearly identical emergency phenotype.

Catatonia changes treatment

A behavioural and motor prodrome may point toward malignant catatonia, for which benzodiazepines and urgent ECT can be decisive.

Common pitfalls

  1. 01

    Waiting for a specific CK threshold before stopping the antipsychotic.

  2. 02

    Missing a depot injection or omitted Parkinson medicine in reconciliation.

  3. 03

    Using antipyretics alone instead of active cooling and supportive care.

  4. 04

    Physically restraining a struggling hyperthermic patient without sedation planning.

  5. 05

    Calling clonus and hyperreflexia lead-pipe rigidity.

  6. 06

    Assuming a culprit medicine excludes sepsis or encephalitis.

  7. 07

    Restarting the same antipsychotic rapidly after apparent recovery.

Practice

Two practice questions

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Question 1 of 2
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NeurologyOriginal SBA

Syndrome after dopamine blockade

Three days after a rapid antipsychotic dose increase, a patient develops confusion, temperature 40 degrees Celsius, severe generalised rigidity, labile blood pressure and a rising creatine kinase. Which diagnosis is most likely?

Choose one answer, then submit
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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • BNF antipsychotic treatment summaryRecognition of NMS and antipsychotic adverse-effect and prescribing cautions.
  • National Poisons Information Service TOXBASECurrent UK emergency toxicology management available to registered clinical services.
  • NICE psychosis and schizophrenia recommendationsAntipsychotic selection, monitoring, adverse reactions and shared treatment decisions.
  • MHRA drug safety updatesUK regulator alerts affecting dopamine antagonists, interactions and severe reactions.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
Supportive intensive care is the foundation. Cooling should be physical because antipyretics do not correct muscle-generated heat. Fluids protect renal perfusion but must be balanced against cardiac or renal failure. Electrolytes and CK guide rhabdomyolysis management. No antidote has high-quality universal evidence. Toxicology, neurology, psychiatry and critical care select dopamine agonism, muscle relaxation or ECT according to severity and the possibility of catatonia.

Key points

  • Neuroleptic malignant syndrome is an idiosyncratic reaction to dopamine-receptor blockade or abrupt withdrawal of dopaminergic treatment, producing altered mental state, generalised rigidity, hyperthermia and autonomic instability.
  • High-potency antipsychotics, rapid dose escalation, parenteral or depot administration, agitation, dehydration and previous NMS increase risk, but any dopamine antagonist can be implicated.
  • Symptoms usually evolve over one to three days rather than within hours: anxiety or confusion and rigidity may precede the peak fever and laboratory injury.
  • Rigidity is typically severe and generalised with reduced or normal reflexes, contrasting with the clonus and hyperreflexia that favour serotonin syndrome.
  • Creatine kinase is often markedly raised from muscle injury, but diagnosis is clinical and an early normal CK does not safely exclude evolving disease.
  • Leucocytosis, transaminase elevation, metabolic acidosis, myoglobinuria and renal injury support severity but are neither specific nor all required.
  • Immediately stop the culprit and other non-essential psychoactive medicines, provide active external cooling, intravenous fluids, thrombosis prevention and organ support.
  • Benzodiazepines reduce agitation and may help overlapping catatonic features; avoid physical restraint where possible because struggle increases heat and rhabdomyolysis.
  • Bromocriptine, amantadine, dantrolene and electroconvulsive therapy have selected roles in severe or refractory cases, but evidence is limited and specialist advice is essential.
  • Restarting antipsychotic therapy should wait until full recovery and use a lower-risk medicine, low dose, slow titration, hydration and close monitoring through psychiatry.
Cultures, imaging and lumbar puncture when indicated
Why
Exclude sepsis, central infection and structural neurological disease.
Interpretation and limitations
Select tests from examination and stability; the existence of a suspect medicine does not eliminate meningitis, pneumonia or aspiration.
  • 06
    ECG and continuous monitoring
    Why
    Detect arrhythmia, electrolyte effects and antipsychotic-associated QT risk.
    Interpretation and limitations
    Correct reversible abnormalities and avoid adding QT-prolonging agents without specialist review.
  • 2ConfirmatoryInvestigate sepsis, encephalitis, heat illness, thyroid disturbance, seizures and rhabdomyolysis in parallel rather than awaiting one confirmatory CK threshold.
  • 3Seek liaison psychiatry, neurology and toxicology input early, because NMS and malignant catatonia can overlap and treatment priorities may change.
    • 03Severe or refractoryAdd specialist-directed therapyRigidity, fever or organ injury remains severe despite exposure withdrawal and supportive care.+
    1. 1Discuss bromocriptine or amantadine for dopamine restoration and dantrolene for extreme rigidity, reviewing enteral access, liver risk and interactions.
    2. 2EscalationEscalate renal, respiratory and coagulation support as needed and reassess occult infection, compartment injury and ongoing depot exposure.
    3. 3Use urgent electroconvulsive therapy when malignant catatonia is likely or severe NMS remains refractory, through anaesthetic and psychiatric emergency governance.
    04Future psychosis careReintroduce treatment cautiously after recoveryNMS has resolved and ongoing psychiatric treatment is necessary.+
    1. 1Wait for full clinical and biochemical recovery and an appropriate washout, reassessing whether antipsychotic medicine remains necessary and discussing alternatives.
    2. 2Choose a lower-risk agent distinct from the culprit, start at a low oral dose, increase slowly and avoid concurrent dehydration, agitation and lithium where possible.
    3. 3Educate patient and carers about early rigidity, fever and confusion, with close physical observations and rapid access to the prescribing team.
    Key medicines and prescribing safety3 treatments · regimens, roles and cautions+
    Reduces agitation and heat-generating motor activity and may treat an overlapping catatonic syndrome.

    Lorazepam

    Use small titrated intravenous or oral doses from the current BNF with airway and respiratory monitoring, especially when agitation or catatonic features are prominent.

    Sedation, aspiration and respiratory depression can obscure deterioration; reduce for frailty and never use it as a substitute for cooling and organ support.

    Attempts to reverse severe dopamine blockade in persistent NMS.

    Bromocriptine

    Specialists may use an enteral dopamine-agonist regimen titrated over several days from toxicology guidance; there is no routine unsupervised ward dose.

    Hypotension, nausea, confusion, psychosis and drug interactions require monitored use; evidence is observational and abrupt withdrawal after longer use is avoided.

    Reduces skeletal-muscle calcium release and may help severe rigidity and temperature generation.

    Dantrolene

    Critical-care and toxicology specialists select an intravenous weight-based regimen for extreme hypermetabolic rigidity using current emergency guidance.

    Weakness, respiratory compromise and hepatotoxicity are important; benefit in NMS is uncertain and it does not replace supportive intensive care.