Dystonic Reaction

Basics

Description

  • Normal pattern of CNS neurotransmission maintained by balance between dopaminergic and cholinergic receptors:
    • Certain drugs antagonize dopamine receptors in the basal ganglia resulting in an imbalance of dopaminergic and cholinergic stimulation
    • This imbalance leads to acute involuntary muscle spasms of the face or neck (the trunk, pelvis, or extremities can also be affected)
  • Although the spasms are uncomfortable and frightening, they are not life threatening except in very rare cases when laryngeal muscles are involved
  • Usually occurs within hours of ingestion:
    • Almost always within first week after exposure to offending drug
  • Risk factors:
    • Children and young adults are at higher risk
    • Rarely occurs in patients >45 yr of age
    • Males more often affected
    • Prior episodes of dystonia significantly increase risk
    • Recent cocaine use increases risk

Etiology

  • Usually occurs after patient has taken antipsychotic, antiemetic, or antidepressant drug
  • Incidence of dystonic reactions varies widely (2–25%) depending on the potency of the agent
  • Higher with more potent drugs (haloperidol, fluphenazine)
  • Lower with less potent drugs (chlorpromazine, thioridazine)
  • Lowest with atypical antipsychotics (quetiapine, olanzapine, risperidone)
  • Antiemetic agents:
    • Metoclopramide (Reglan)
    • Prochlorperazine (Compazine)
    • Promethazine (Phenergan)
    • Droperidol (Inapsine)
  • Other agents:
    • Cyclic antidepressants
    • H2 blockers
    • Some antimalarial agents
    • Antihistamines
    • Some anticonvulsants
    • Doxepin
    • Lithium
    • Phencyclidine
    • Cocaine

Pediatric Considerations
Children are particularly vulnerable to dystonic reactions when dehydrated or febrile

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