Validation of the American Association of Poison Control Centers out of hospital guideline for pediatric diphenhydramine ingestions.

Context: In 2006, the American Association of Poison Control Centers (AAPCC) published an out of hospital guideline for diphenhydramine overdoses in children. This guideline has not been validated.

Objective: Our objective was to determine the incidence of serious clinical effects or use of medical treatments after unintentional diphenhydramine ingestions in children. We sought to determine if patients with less than 7.5 mg/kg ingestions developed medical complications of diphenhydramine toxicity.

Materials And Methods: In our observational case series, we searched 7 years of data (2000-2006) in the Texas Poison Center Network for diphenhydramine using the AAPCC generic codes. We included only acute, single ingestions of diphenhydramine in children under 6 years old. We included only patients with a recorded weight, known amount of ingestant, and known follow-up. We defined "serious clinical effects" as hallucinations, seizure, wide QRS on electrocardiogram, wide complex dysrhythmia, any conduction block, hypotension, hypertension, rhabdomyolysis, pyrexia, dystonia, coma, respiratory depression, or death. One trained abstractor reviewed the data and entered it into an electronic data collection form. Twenty percent of the charts were audited for abstractor agreement.

Results: Our search resulted in 928 cases. Of these, 305 were included in our study. Of the patients who ingested doses less than 7.5 mg/kg, 99.7% (299/300) did not require critical treatments or were without serious clinical effects. One child was admitted. Five children ingested doses of more than 7.5 mg/kg. All five were observed in the emergency department and discharged home. Two patients had serious clinical effects of hallucinations, one of which ingested more than 7.5 mg/kg. No child required critical treatments. Our agreement on chart review for 20% of the cases was very good for "serious clinical effects" (kappa, 0.79; 95% CI, 0.39-1.0) and excellent for "critical treatments" (kappa, 1.0).

Conclusion: Based on our observational case series, 99.6% of patients who reportedly ingested doses less than 7.5 mg/kg did not develop serious clinical effects or require admission. Pediatric ingestions over 7.5 mg/kg were uncommon in our study population. Serious clinical effects, critical treatments, and admission from diphenhydramine were rare in children under 6 years old.