Pharmakokinetics and Pharmacodynamics of Hydroxyzine in Healthy Dogs

Atopic dermatitis is a common allergic skin disease in dogs and humans. Antihistamines are among the most commonly prescribed treatments. Unfortunately, the optimal dosages of commonly used antihistamines have never been scientifically determined, and their effects have not been validated in dogs. Researchers at North Carolina State University wanted to determine whether hydroxyzine, one of the drugs most commonly used to treat atopic dermatitis in dogs, truly provides an antihistamine effect and, if so, what the appropriate dose is for dogs.

Results

The researchers successfully determined that hydroxyzine does produce an antihistamine effect and confirmed that a twice-daily dose is appropriate, versus the previously standard prescription of three times a day. They also discovered that when hydroxyzine is administered orally or intravenously the drug breaks down into its simpler form (cetirizine), and this simpler form is responsible for the actual antihistamine effect. They now want to look at this drug as a more effective treatment for atopic dermatitis.

Co-sponsored with the Morris Animal Foundation, Grant Number: D07CA-029

Thierry Olivry
DrVet, PhD, Dip. ECVD, Dip. ACVD
North Carolina State University