How to manage lockjaw induced by Compazine (prochlorperazine)?

Management of Prochlorperazine-Induced Lockjaw (Dystonic Reaction)

Immediate administration of intravenous or intramuscular anticholinergic medication such as benztropine 1-2 mg is the most effective treatment for prochlorperazine-induced lockjaw (acute dystonic reaction). 1

Pathophysiology and Recognition

Prochlorperazine (Compazine) is a phenothiazine antiemetic that can cause acute dystonic reactions, including lockjaw (trismus), which is a form of extrapyramidal symptom (EPS). These reactions occur in approximately 4% of patients receiving prochlorperazine in the emergency department setting. 2

Key characteristics of prochlorperazine-induced lockjaw:

• Sudden onset of jaw muscle rigidity
• Difficulty opening mouth
• May be accompanied by other dystonic symptoms (neck spasms, oculogyric crisis)
• Typically occurs within hours to days of medication administration
• More common in young adults 3

Treatment Algorithm

First-Line Treatment:

1. Anticholinergic agents:

   • Benztropine (Cogentin): 1-2 mg IV/IM as a single dose 1
   • Relief typically occurs within minutes
   • May repeat dose if symptoms persist after 15 minutes

2. Alternative agents if benztropine is unavailable:

   • Diphenhydramine (Benadryl): 25-50 mg IV/IM
   • Orphenadrine (Dispal): IM administration (particularly effective in children) 4

Adjunctive Therapy:

• Diazepam: 5-10 mg IV/PO to help with muscle relaxation 5
• Discontinue prochlorperazine immediately

Follow-up Care:

• Continue oral anticholinergic medication for 48-72 hours to prevent recurrence
• Benztropine 1-2 mg PO BID for 2-3 days
• Avoid prochlorperazine and other phenothiazines in the future

Special Considerations

• Monitor respiratory status, as severe dystonic reactions may involve laryngeal muscles
• Document the reaction as a medication allergy to prevent future exposure
• Consider alternative antiemetics for future use:
  • Ondansetron: 4-8 mg IV/PO
  • Metoclopramide (with prophylactic diphenhydramine to prevent EPS)
  • Granisetron or other 5-HT3 antagonists 6

Risk Factors for Dystonic Reactions

Patients at higher risk for developing prochlorperazine-induced dystonia include:

• Young adults
• Concurrent viral infections 3
• Previous history of dystonic reactions
• Dehydration
• Higher doses of medication

Prevention

For patients who require phenothiazine therapy but have experienced dystonic reactions:

• Pre-medicate with anticholinergics (benztropine 1-2 mg) or antihistamines (diphenhydramine 25-50 mg)
• Use lower doses of phenothiazines
• Consider alternative antiemetic classes

Common Pitfalls

1. Misdiagnosing dystonic reaction as anxiety, seizure, or tetanus
2. Failing to recognize the medication as the cause of symptoms
3. Not providing prophylactic anticholinergic therapy for 48-72 hours after initial treatment, which may lead to symptom recurrence
4. Continuing the offending agent despite symptoms

Remember that prompt recognition and treatment of prochlorperazine-induced lockjaw is essential to relieve patient distress and prevent progression to more severe dystonic reactions involving respiratory muscles.