Correspondence

Chronic Urticaria and Angioedema

N Engl J Med 2002; 347:1724November 21, 2002

Article

To the Editor:

In his letter to the editor, Kaplan (July 18 issue)1 suggests that cetirizine is one of the active ingredients of hydroxyzine. It is not, although their chemical structures are similar.

Stanley Scheindlin, D.Sc.
3011 Nesper St., Philadelphia, PA 19152

1 References

1. 1

   Kaplan AP. Chronic urticaria and angioedema. N Engl J Med 2002;347:222-222
   Full Text | Web of Science

Author/Editor Response

Dr. Kaplan replies:

To the Editor: My statement regarding the relation of cetirizine to hydroxyzine warrants clarification. Cetirizine is the active metabolite (not ingredient) of hydroxyzine, and as such, cetirizine is responsible for much of the histamine H₁–receptor blockade associated with the use of hydroxyzine, even though hydroxyzine has H₁-receptor–binding activity in vitro.

Allen P. Kaplan, M.D.
Medical University of South Carolina, Charleston, SC 29425
kaplana@musc.edu