Neuroleptic malignant syndrome (NMS) is a rare, potentially life threatening disorder most frequently caused by the use of drugs that block dopamine. Dopamine is a neurotransmitter (or messenger) in the brain that is essential to the normal functioning of the central nervous system. NMS results in dysfunction of the autonomic nervous system, which regulates involuntary actions such as the heart rate, blood pressure, sweating and digestion.
Up to 12 percent of patients using neuroleptic medications are thought to develop NMS. NMS can begin at almost any time after the drug dose is given or increased, but it usually develops from between 4-14 days after drug treatment is initiated or stepped-up.
Neuroleptic or antipsychotic drugs associated with NMS include:
- prochlorperazine (Chlorazine, Compazine)
- promethazine (Phenergan, Atosil, Avomine, Fargan, Farganesse, Promethegan, Prothiazine, Romergan)
- olanzapine (Zyprexa)
- clozapine (Clozaril)
- risperidone (Risperdal)
Other dopamine blocking medications associated with NMS include:
- metoclopramide (Maxolon, Reglan, Degan, Maxeran, Primperan, Pylomid)
- amoxapine (Ascendin)
- lithium
Medications used to treat Parkinson’s such as levodopa (Sinemet), amantadine (Symmetrel), and bromocriptine (Parlodel) can also precipitate NMS when withdrawn too quickly.
Symptoms of NMS may include:
- Muscle rigidity (usually the first symptom to develop)
- High fever/hyperthermia
- Unstable blood pressure
- Tachycardia (fast heart beat)
- Tachypnea (fast breathing)
- Heavy sweating
- Tremor
- Impaired consciousness (including agitation and delirium)
- Catatonia
- Coma
Due to improved monitoring and recognition of NMS, mortality rates have dropped to from 5 – 12 percent. Once symptoms do appear, however, they progress quickly, and aggressive treatment is needed rapidly to prevent cardiovascular and respiratory collapse. Unfortunately, symptoms continue to be misinterpreted, delaying treatment.
Treatment involves removal of the causative agent, plenty of fluids, supplemental oxygen, and cooling. In intractable or severe cases of psychosis or catatonia after other symptoms of NMS have abated, electroconvulsive therapy may be necessary. Medications that may be employed include:
- Bromocriptine or amantadine – to restore dopamine levels
- Dantrolene – to resolve hyperthermia and muscle rigidity
- Benzodiazepines – to treat agitated patients and help relax muscles and reverse catatonia