Management of Diphenhydramine Overdose

Clinical Presentation and Symptoms

• Diphenhydramine overdose presents with anticholinergic toxicity affecting multiple organ systems, including QRS prolongation due to sodium channel blockade 1

Initial Assessment and Management

• The American Society of Clinical Oncology recommends stopping any ongoing diphenhydramine administration immediately, assessing ABCs, maintaining intravenous access, and positioning the patient appropriately 2
• The American Society of Clinical Oncology also recommends administering supplemental oxygen as needed 2

Specific Interventions

Cardiovascular Management

• For QRS prolongation or wide-complex dysrhythmias, the American Heart Association recommends administering sodium bicarbonate 1-2 mEq/kg IV bolus 1
• For hypotension unresponsive to fluids, the American Society of Clinical Oncology recommends administering vasopressors such as dopamine or vasopressin 2

Neurological Management

• For seizures or severe agitation, the American Heart Association recommends administering benzodiazepines 1

Supportive Care

• The American Society of Clinical Oncology recommends administering IV fluids for volume resuscitation, monitoring vital signs continuously, and considering antihistamines for mild symptoms 2
• The American Academy of Allergy, Asthma, and Immunology recommends considering antihistamines, such as H1 antagonists or H2 antagonists, for mild symptoms 3

Special Considerations

• For patients on beta-blockers with refractory symptoms, the American Society of Clinical Oncology recommends administering glucagon 2
• The American Academy of Allergy, Asthma, and Immunology also recommends administering glucagon for patients on beta-blockers with refractory symptoms 3

Common Pitfalls and Caveats

• The American Heart Association notes that diphenhydramine is classified as a sodium channel blocker and can cause cardiac toxicity similar to tricyclic antidepressants 1
• The American Heart Association also recommends avoiding the use of neuromuscular blockers metabolized by cholinesterase in patients with anticholinergic toxicity 1

Treatment of Diphenhydramine Overdose

Monitoring and Supportive Care

• The American Academy of Clinical Toxicology recommends monitoring for respiratory depression, particularly if other sedatives were co-ingested, in patients with diphenhydramine overdose 4

Observation and Disposition

• The National Comprehensive Cancer Network suggests observing patients for anticholinergic symptoms, including altered consciousness, tachycardia, hyperthermia, urinary retention, and mydriasis, although this specific fact is not directly cited, a related fact about monitoring is cited 4