SELECTED ARTICLES FROM THE RECENT LITERATURE 2008 5/21/2008 Pharmacodynamic Effects of Intramuscular Diphenhydramine, Oral Diphenhydramine, and Oral Fexofenadine as Assessed by Histamine Skin Test Suppression Summary The authors utilized 18 healthy subjects for a double-blind, placebo-controlled, three-way, randomized, crossover study to compare the pharmacodynamic effects of fexofenadine 180 mg orally, diphenhydramine 50 mg orally, and diphenhydramine 50 mg administered intramuscularly. They used the suppression of histamine-induced skin tests as an endpoint to assess the pharmacodynamic profile of these agents. The major observations were that intramuscular diphenhydramine was, as expected, more effective than oral agents in the first 60 minutes. Oral diphenhydramine also tended to work more rapidly than fexofenadine in the first 60 minutes. After the first hour differences between oral diphenhydramine and oral fexofenadine were not statistically significant. They concluded that since there did not appear to be any clinically significant differences between diphenhydramine and fexofenadine the non-sedating drug was preferabe Reference Jones DH, et al. Time dependent inhibition of histamine-induced cutaneous responses by oral and intramuscular diphenhydramine and oral fexofenadine. Annals of Allergy, Asthma, and Immunology 2008; 100:452-456.   © Copyright 1997-2008 American Academy of Allergy, Asthma and Immunology All rights reserved