What is the management for Benadryl (diphenhydramine) intoxication?

Management of Diphenhydramine Intoxication

The management of diphenhydramine intoxication requires immediate supportive care, sodium bicarbonate administration for cardiotoxicity, and specific interventions based on symptom severity.

Initial Assessment and Stabilization

• Immediately assess ABCs (Airway, Breathing, Circulation) and level of consciousness 1
• Maintain IV access throughout treatment 1
• Position the patient appropriately based on symptoms:
  • Trendelenburg position for hypotension
  • Sitting up for respiratory distress
  • Recovery position if unconscious 1
• Administer oxygen as needed 1

Cardiac Monitoring and Management

• Obtain ECG to assess for QRS prolongation and terminal rightward axis deviation (in lead aVR) 1
• Administer sodium bicarbonate for life-threatening cardiotoxicity:
  • Give as bolus IV administration of hypertonic solutions (1000 mEq/L in adults, 500 mEq/L in children) 1
  • This is a Class 1 recommendation (strong evidence) for treating sodium channel blockade 1

Specific Interventions Based on Symptoms

For Mild to Moderate Symptoms

• Drowsiness, anticholinergic signs (dry mouth, blurred vision), tachycardia 2
• Monitor vital signs every 30 minutes during initial treatment, then hourly for 4 hours 1
• Provide supportive care and observation

For Severe Symptoms (doses >1.0g)

• Delirium/psychosis, seizures, coma 2
• Administer benzodiazepines for seizures or agitation 3
• Consider early endotracheal intubation for airway protection in severe cases 1
• Avoid succinylcholine as a neuromuscular blocker due to potential interactions 1

Gastrointestinal Decontamination

• Do not induce emesis due to risk of rapid deterioration 3
• Activated charcoal may be considered if the patient presents early (within 1 hour) and has no risk of rapid deterioration in mental status 3

Advanced Interventions for Refractory Cases

• Consider extracorporeal life support (VA-ECMO) for refractory cardiac arrest due to severe diphenhydramine toxicity 1
• Physostigmine should be reserved for hospital administration only, not in pre-hospital settings 3

Monitoring and Disposition

• Close observation for 24 hours is recommended after severe reactions 1
• Monitor vital signs and recurrence of symptoms 1
• Document the intoxication episode including pre-treatment assessments, description and grading of symptoms, and management provided 1

Critical Considerations and Pitfalls

• Diphenhydramine is classified as a sodium channel blocker that can cause QRS prolongation, hypotension, seizures, and cardiovascular collapse 1
• Severe toxicity typically occurs with doses above 1.0g, with critical symptoms including delirium/psychosis, seizures, and coma 2
• Fatal outcomes are rare but can occur with massive overdoses (documented case with 7.5g) 4
• The dose-dependent toxicity pattern shows moderate symptoms above 0.3g and severe symptoms above 1.0g 2
• Avoid medications that may worsen anticholinergic toxicity or further depress the CNS

By following this structured approach to diphenhydramine intoxication management, focusing on cardiac monitoring, sodium bicarbonate administration for cardiotoxicity, and appropriate supportive care, clinicians can effectively manage this potentially life-threatening condition.