Tuesday, November 8, 2016

Acute Dystonic Reaction : Treatment

  • An acute dystonic reaction, usually transient, is a recognized complication of the dopamine receptor-blocking drugs, such as the antipsychotics (eg, haloperidol, chlorpromazine) and antiemetics (eg, phenothiazines, metoclopramide)
  • Dystonic reactions also can occur with levodopa, anticonvulsants, antidepressants (eg, selective serotonin reuptake inhibitors), and ergots.
Treatment
  • The offending drug should be discontinued.
  • Treatment of acute dystonia with antihistamine or anticholinergic medications is usually rapidly effective
Diphenhydramine
  • IV diphenhydramine (1 to 2 mg/kg per dose, maximum dose 50 mg) is used most frequently
  • Diphenhydramine may also be given intramuscularly but the onset of action is delayed compared with intravonicenous administration.
  • Typically results in resolution of an acute dystonic reaction within minutes.
  • Muscle relaxation begins within 30 minutes and but may not complete for 90 minutes when the antidote is given as IM or Oral
  • Intravenous administration is preferred over oral administration for initiation of treatment because patients may have difficulty swallowing.
  • Parenteral administration is required for life-threatening dystonia with associated laryngospasm or stridor
  • Once the acute dystonic reaction is treated, diphenhydramine is given orally (1.25 mg/kg per dose) every six hours for one to two days to prevent recurrence or 12.5-50mg TDS-QID for 3 days
  • In some cases, however, a single dose of oral diphenhydramine or trihexyphenidyl suffices.
Benzodiazepams
  • Some recommend using diazepam for patients with dystonic reactions refractory to anticholinergic therapy or when such therapy is contraindicated
  • Diazepam and lorazepam are favoured because of their longer duration of action
  • IV diazepam can be given in 5-mg increment every 5 minutes as needed for reversal
  • lorazepam 1 to 2 mg IV in adults; 0.05 mg/kg IV in children or 2mg every 5 minute as needed
Others
  • Antihistamine, benzodiazepines, beta-adrenergic antagonists (propranolol), beta-adrenergic agonists (clonidine), or dopamine agonists (amantadine) may also be used
  • amantadine (100 mg orally twice or three times daily in adults), or biperiden (2 mg orally in adults). At least two controlled studies have shown amantadine to be as effective as anticholinergic therapy, with fewer side effects
  • Propranolol (20 to 40 mg initial dose) reduces involuntary movements in akathisia, but does not reduce anxiety
  • A randomized trial of 13 patients with acute akathisia from antipsychotic medications reported a benefit from trazodone (100 mg/day orally in adults)
  • Patients treated with dopamine receptor-blocking agents occasionally develop persistent tardive dystonia after the offending drug is stopped.
  • If no spontaneous improvement occurs, they may respond to trials of muscle relaxants, anticholinergic drugs, and tetrabenazine
References:
  1. www.uptodate.com
  2. www.lexicomp.com
  3. Harwood-Nuss' Clinical Practice of Emergency Medicine
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3460160/
  5. http://emedicine.medscape.com/article/814632-medication

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