What is neuroleptic malignant syndrome (NMS)?

Neuroleptic malignant syndrome (NMS): 

The neuroleptic malignant syndrome is a rare but life-threatening condition that can occur with any antipsychotic drugs (both typical and atypical). It is most common when starting a treatment or increasing the dose. It occurs in 0.2% of patients on neuroleptic drugs, particularly the potent dopaminergic antagonists, such as haloperidol, either alone or with other drugs especially lithium carbonate. NMS can also be precipitated by the abrupt withdrawal of dopaminergic medications in Parkinson’s disease (PD) patients.

Clinical features: 

• Symptoms occur within a few days to a few weeks of starting treatment with antipsychotics. 
• Symptoms include fever, tremor, muscle rigidity, confusion, delirium and impaired consciousness (fluctuating level of consciousness). 
• Autonomic instability is well recognized and is associated with excessive sweating, labile blood pressure and tachycardia. 

Investigations: 

• Characteristic laboratory findings are an elevated creatinine phosphokinase, leukocytosis and abnormal liver biochemistry. 

Consequences:

• Rhabdomyolysis, found in NMS, may precipitate acute renal failure. 
• Pulmonary embolus and death
• Mortality is as high as up to 20% in untreated cases. But with treatment, it comes down to 5%.

Managements:

• The management of this condition involves stopping the neuroleptic drug immediately, antipyretics and rehydration. 
• The drug dantrolene (reduce muscle tone) and Bromocriptine (enhances dopaminergic activity) may be useful in some cases. 
• Doses: bromocriptine 2.5 mg (o) bd, gradually increasing to 5 mg (o) TDS and dantrolene 50 mg IV every 12 hours for up to 7 doses

Additional: Available antipsychotic drugs

Sources:

• Rapid Review of Clinical Medicine for MRCP Part 2 Second Edition by Sanjay Sharma; Q 209
• Step Up to MRCP Review Note for Part I & Part II by Dr Khaled El Magraby; page: 991
• MRCP, The Only Notes You Will Ever Need, 4th edition; SudaMediCa Publications; page: 470
• Davidsons Principles and Practice of Medicine 23 edition; page: 1197
• Kumar & Clark’s Clinical Medicine 9e (2016); page: 925
• John Murtagh’s General Practice-6th Edition; page: 517, 602
• Harrison’s Principles of Internal Medicine 2 volumes 19th Edition; page: 2624
• Pharmacological Classification of Drugs with Doses and preparations 5th Edition by KD Tripathi; page: 75 (image)