What amount of Benadryl (diphenhydramine) ingestion in a healthy 14-year-old female would require hospital admission?

Hospital Admission Threshold for Diphenhydramine Ingestion in a 14-Year-Old Female

Any 14-year-old who ingests 7.5 mg/kg or 300 mg of diphenhydramine (whichever is less) should be referred to an emergency department for evaluation and potential admission. 1

Specific Dosing Thresholds for Admission

For a patient 6 years of age and older (which includes your 14-year-old):

• Ingestion of ≥7.5 mg/kg of diphenhydramine requires emergency department referral 1
• Ingestion of ≥300 mg of diphenhydramine requires emergency department referral (whichever threshold is reached first) 1

Example calculation: For a 50 kg (110 lb) adolescent, the threshold would be 300 mg (not 375 mg), since 300 mg is the lower cutoff. For a 30 kg adolescent, the threshold would be 225 mg (7.5 mg/kg).

Symptom-Based Criteria Requiring Immediate Referral

Regardless of dose ingested, immediate emergency department referral is mandatory if the patient exhibits: 1

• Agitation or behavioral changes beyond mild drowsiness
• Staring spells or inconsolable crying
• Hallucinations
• Abnormal muscle movements or seizures
• Loss of consciousness or altered mental status
• Respiratory depression
• Cardiac conduction abnormalities (QRS widening >0.10 msec) 1

Observation Timeline and Safe Discharge Criteria

If the ingestion is below the toxic threshold (< 7.5 mg/kg and < 300 mg) and the patient remains asymptomatic: 1

• The patient can be observed at home if more than 4 hours have elapsed since ingestion with no symptoms developing 1
• Poison center follow-up should occur at approximately 4 hours post-ingestion 1
• If symptoms develop at any point during observation, immediate emergency department referral is required 1

Critical Complications Requiring Admission

Once in the emergency department, admission is typically required for: 2, 3, 4

• Seizure activity (documented complication in overdose) 2, 3, 4
• Cardiac conduction abnormalities including QRS widening or QT prolongation 2, 3
• Hemodynamic instability or cardiac complications 2, 4
• Rhabdomyolysis (rare but documented complication) 3
• Coma or severe altered mental status 4
• Anticholinergic toxidrome requiring ongoing monitoring 2

Special Considerations for Adolescents

Intentional ingestions in this age group carry higher risk: 4

• Adolescent diphenhydramine ingestions increased significantly between 2007-2020, with more serious outcomes observed 4
• Suspected suicide attempts with diphenhydramine are associated with cardiac complications, seizures, coma, and death at higher rates than misuse or abuse 4
• Any ingestion with suicidal intent requires emergency department referral regardless of dose 1
• Fatal outcomes have been documented in adolescents, including a 14-year-old girl who died after ingesting 7.5 g of diphenhydramine 2

Prehospital Management Restrictions

Do not administer the following before hospital arrival: 1

• Do not induce emesis 1
• Do not give activated charcoal en route due to risk of loss of consciousness or seizures 1
• Benzodiazepines may be given by EMS for agitation or seizures if authorized by medical direction 1
• Sodium bicarbonate may be given by EMS for QRS widening if authorized by medical direction 1

Common Pitfall to Avoid

The most dangerous error is underestimating the toxicity of diphenhydramine because it is available over-the-counter. 2, 4 Fatal outcomes occur in adolescents, and the threshold for emergency evaluation (300 mg or 7.5 mg/kg) is relatively low—equivalent to just 12 standard 25 mg tablets. 1, 2