Pfizer Zyrtec comparative onset of action claims "appear to be substantiated" -- FDA ad letter.
Executive Summary
PFIZER ZYRTEC ONSET OF ACTION COMPARISONS "APPEAR TO BE SUBSTANTIATED," FDA told the company in an April 28 letter from the Division of Drug Marketing, Advertising & Communications. The letter cites a pair of two-day trials comparing the Pfizer product to Schering-Plough's Claritin in terms of onset of antihistamine activity: a Journal of Allergy and Clinical Immunology study by Meltzer et al. and an unpublished study from a controlled environmental exposure unit.