| Clinical and laboratory features |
- Affected patients have recent exposure to dopamine antagonist (eg, antipsychotic or antiemetic agent) or dopamine agonist withdrawal
- Patients demonstrate:
- Mental status change, which may manifest as an agitated or hypoactive delirium
- Muscular rigidity that is generalized and "lead pipe" in nature
- Hyperthermia, temperatures above 38°C, sometimes higher than 40°C
- Autonomic instability manifesting as tachycardia, labile blood pressure, tachypnea; arrhythmias may occur
- Elevated serum creatine kinase is typical
- NMS is a clinical diagnosis; no laboratory test can confirm the diagnosis
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| Evaluation |
- The following tests may be helpful to narrow the differential diagnosis and to monitor potential complications:
- Complete blood count, basic electrolytes, creatinine, BUN, calcium, magnesium, phosphorus
- Creatine kinase (CK), hepatic transaminases, lactate dehydrogenase, alkaline phosphatase
- Blood culture, urinalysis, urine myoglobin, urine culture
- Blood and urine toxicology screen
- Chest radiograph
- Electrocardiogram
- Head computed tomography, lumbar puncture, electroencephalography
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| Differential diagnosis |
- Serotonin syndrome
- Malignant hyperthermia
- Malignant catatonia
- Anticholinergic overdose or poisoning
- Acute intoxication with cocaine, ecstasy, or methamphetamines
- Meningitis or encephalitis
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| Treatment |
- Discontinue dopamine antagonist therapy (or resume dopamine agonist in case of withdrawal)
- Stop potential contributing agents (lithium, anticholinergic therapy, serotonergic agents)
- Maintain cardiorespiratory stability, cardiorespiratory monitoring, mechanical ventilation, antiarrhythmic drugs
- Maintain euvolemia; if CK is very elevated, use high-volume IV isotonic saline
- Treat hyperthermia with cooling blankets; ice water gastric lavage and axillary ice packs if required
- Use benzodiazepines to control agitation, if necessary
- For moderate to severe NMS, give benzodiazepines (eg, lorazepam 1 to 2 mg IM or IV every 4 to 6 hours) for agitation and muscle rigidity
- Dantrolene (eg, 1 to 2.5 mg/kg IV) may be added for moderate to severe muscle rigidity with elevated CK
- Bromocriptine or amantadine may be added for moderate to severe symptoms
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