NMS

Serotonin syndrome

Catatonia

Dopamine blockade causing hypothalamic dysfunction

Serotonergic agonism in central and peripheral nervous system secondary to:

– Decreased serotonin breakdown

– Decreased serotonin reuptake

– Increased serotonin precursors or agonists

– Increased serotonin release

– Drug-drug interactions

GABA receptor dysfunction vs movement disorder

– ≥1 antipsychotic use

– Parenteral antipsychotics

– Titration of antipsychotics

– Cessation of dopaminergic agents

– Young age

– Dehydration

– Malnutrition

– Dementia

– >1 serotonergic agent (table 16.2-4)

– Older age (drug metabolism)

– Bipolar and major depressive disorders

– Psychotic disorders

– Systemic medical disorders

– Abrupt discontinuation of benzodiazepines

– Hyperthermia (≥38 degrees Celsius)

– Autonomic instability (hypertension, tachycardia, tachypnea, hypoxia)

– Altered mental status (delirium, stupor, coma)

– Muscular rigidity (“lead pipe,” resistant to anticholinergic treatment)

– Tremor

– Sialorrhea

– Akinesia

– Dystonia

– Trismus

– Myoclonus

– Dysarthria

– Dysphagia

– Pallor

– Rhabdomyolysis

– Hyperthermia (moderate <40 degrees Celsius; severe >40 degrees Celsius)

–Altered mental status (agitation, restlessness, anxiety, delirium, confusion, coma)

– Autonomic instability (hypertension, tachycardia, diaphoresis, mydriasis, hyperactive bowel sounds, GI upset [nausea, vomiting, diarrhea])

– Neuromuscular hyperactivity (hyperreflexia [lower extremities], myoclonus, tremor, opsoclonus, spontaneous or inducible clonus [lower extremities], respiratory failure, tonic-clonic seizures)

≥3 symptoms of:

– Stupor

– Cataplexy

– Waxy flexibility

– Mutism

– Negativism

– Posturing

– Mannerisms

– Stereotypy

– Agitation

– Grimacing

– Echolalia

– Echopraxia

– Discontinue antipsychotic

– Supportive treatment

– Dopamine agonist: bromocriptine, amantadine

– Muscle relaxant: dantrolene

– Electroconvulsive therapy

– Discontinue serotonergic agent

– Supportive treatment

– Benzodiazepine: lorazepam

– Antihistamine: cyproheptadine

– Benzodiazepine: lorazepam

– Electroconvulsive therapy

Differentiating features of NMS and serotonin syndrome:

1) Bowel sounds: Normal or decreased (NMS) vs hyperactive (serotonin syndrome).

2) Reflexes: Slow, depressed (NMS) vs hyperreflexia, clonus (serotonin syndrome).

3) Muscle rigidity: Increased rigidity in all muscle groups (NMS) vs increased rigidity primarily in lower extremities (serotonin syndrome).