What are the causes of acute dystonic reactions?

From the Guidelines

Acute dystonic reactions are primarily caused by medications that block dopamine receptors in the brain, particularly antipsychotics and antiemetics, such as metoclopramide and prochlorperazine, as noted in the guidelines for antiemesis 1. The most common causes of acute dystonic reactions include:

• First-generation antipsychotics like haloperidol, chlorpromazine, and fluphenazine
• Antiemetics such as metoclopramide, prochlorperazine, and promethazine These reactions typically occur within hours to days of starting the medication or increasing the dose. Risk factors for acute dystonic reactions include:
• Young age, especially males under 30, as mentioned in the practice parameter for the assessment and treatment of children and adolescents with schizophrenia 1
• Higher medication doses
• Previous dystonic reactions
• Dehydration The mechanism involves an imbalance between dopamine and acetylcholine in the basal ganglia, where dopamine blockade leads to relative acetylcholine excess, causing abnormal muscle contractions. Treatment involves immediate administration of anticholinergic medications like benztropine (1-2 mg IV/IM) or diphenhydramine (25-50 mg IV/IM), which usually resolves symptoms within minutes, as recommended in the guidelines for antiemesis 1. Prevention strategies include using lower doses of high-risk medications, switching to atypical antipsychotics with lower dystonia risk, or prophylactic anticholinergic medication in high-risk patients. It is essential to monitor patients for dystonic reactions when using prochlorperazine or metoclopramide, and diphenhydramine can be used for dystonic reactions, while benztropine may be used in patients who are allergic to diphenhydramine, as noted in the guidelines for antiemesis 1.

From the FDA Drug Label

Acute dystonic reactions occur in approximately 1 in 500 patients treated with the usual adult dosages of 30 to 40 mg/day of metoclopramide These usually are seen during the first 24 to 48 hours of treatment with metoclopramide, occur more frequently in pediatric patients and adult patients less than 30 years of age EPS during the administration of haloperidol have been reported frequently, often during the first few days of treatment. EPS can be categorized generally as Parkinson-like symptoms, akathisia, or dystonia (including opisthotonos and oculogyric crisis) Dystonic symptoms include: spasm of the neck muscles, sometimes progressing to tightness of the throat, swallowing difficulty, difficulty breathing, and/or protrusion of the tongue An elevated risk of acute dystonia is observed in males and younger age groups

The causes of acute dystonic reactions include:

• Medications: Such as metoclopramide and haloperidol
• Age: More frequent in pediatric patients and adult patients less than 30 years of age
• Dose: Higher doses of metoclopramide increase the risk of acute dystonic reactions
• Gender: An elevated risk of acute dystonia is observed in males
• Time of treatment: Usually seen during the first 24 to 48 hours of treatment with metoclopramide, and often during the first few days of treatment with haloperidol 2 3

From the Research

Causes of Acute Dystonic Reactions

• Acute dystonic reactions can be caused by various medications, including:
  • Antipsychotic drugs such as haloperidol 4
  • Anti-emetic medications like metoclopramide 4, 5
  • Atypical antipsychotics, although the risk is minimal 6
  • Benzodiazepines like diazepam 7
• These reactions can occur after a single dose or after prolonged use of the medication
• Certain patient populations are more prone to developing acute dystonic reactions, including:
  • Female patients
  • Children
  • Older patients
  • Patients receiving high doses of metoclopramide 5
• Acute dystonic reactions can be life-threatening and should be detected early to prevent complications

Medication-Induced Dystonic Reactions

• Medications can induce dystonic reactions through various mechanisms, including:
  • Blockade of dopamine receptors in the brain
  • Alteration of neurotransmitter balance
• The risk of developing a dystonic reaction can be increased by:
  • High doses of medication
  • Prolonged use of medication
  • Individual patient susceptibility

Clinical Presentation

• Acute dystonic reactions can present with a range of symptoms, including:
  • Torticollis
  • Tongue protrusion
  • Respiratory distress
  • Abnormal postures
• These symptoms can be severe and require immediate medical attention to prevent complications 4, 5