SHIFTING PERSPECTIVES: DIPHENHYDRAMINE USAGE IN ANAPHYLAXIS AND URTICARIA ACROSS UNITED STATES EMERGENCY DEPARTMENTS

Introduction

In recent years, there has been a notable shift in the medical community's perspective regarding the use of diphenhydramine for allergic reactions, specifically for urticaria and anaphylaxis, stemming from its side effect profile and superior efficacy of second-generation antihistamines. Notably, the AAAAI's updated 2020 anaphylaxis guidelines recommended against use of first-generation antihistamines in the acute phase or to prevent biphasic reactions. Our study aimed to assess diphenhydramine utilization in US emergency departments (EDs) for anaphylaxis and urticaria from 2019 to 2021.

Methods

We conducted a cross-sectional study using data from the 2019-2021 National Hospital Ambulatory Medical Care Survey (NHAMCS) for patient visits to emergency departments. We analyzed individuals with ICD-10 codes for anaphylaxis (T78) and/or urticaria (L50) who received at least one medication. The NHAMCS is conducted by the CDC and includes demographics, reasons for visits, diagnoses, treatments, and outcomes. Significance was determined using design-based Pearson chi-square with P<0.050.

Results

Of 450 anaphylaxis and/or urticaria cases, 276 involved diphenhydramine use which after sampling weights were applied represented 62.0% of cases. Diphenhydramine administration rates were 58.0% for anaphylaxis alone, 69.5% for urticaria alone, and 73.4% for individuals presenting with both conditions. No significant change in diphenhydramine use was observed from 2019 to 2021 (P=0.9421).

Conclusion

Despite emerging evidence and evolving clinical guidelines regarding diphenhydramine use, our findings suggest no discernible changes in ED practices post-AAAAI updates. Moving forward, bridging this gap between evidence-based guidelines and clinical practice is imperative for enhancing patient care and ensuring adherence of evolving standards in urticaria and anaphylaxis management.