TAGAMET "GREATER SAFETY" CLAIM OVER ZANTAC IS "UNSUBSTANTIATED"

TAGAMET "GREATER SAFETY" CLAIM OVER ZANTAC IS "UNSUBSTANTIATED" by clinical studies, FDA said in a recent letter to SmithKline seeking immediate cancellation of the ad campaign. The Aug. 4 letter focused on a promotional campaign of print ads, detail information and letters to physicians. The agency noted the superiority claim is based in part on the assertion that, in contrast to Glaxo's Zantac (ranitidine HCl), Tagamet reduces the potential risk of prolonged acid suppression. The statement is "false and misleading," FDA stated. "We are unaware of any properly designed clinical studies which support this comparative safety message." In response, SK&F agreed to halt the promotional campaign and to modify future promotions in compliance with FDA's position. New ads for Tagamet are scheduled to break "shortly," the company said. The letter from FDA's Division of Drug Advertising and Labeling noted that the comparative Tagamet ads made claims for "greater safety for hospitalized ulcer patients," "lower risk of hepatotoxicity than Zantac" and "greater safety for ulcer patients on acetaminophen." The ads appeared this summer in medical journals, including The New England Journal of Medicine and JAMA. Ads were pulled after September issues. In support of claims that "unlike Zantac, Tagamet has been shown to inhibit the formation of toxic acetaminophen metabolites," FDA asserted that SK&F "primarily relies for its comparative claim on selected in vitro and animal studies." Further, the agency added: "there are no clinical data referenced which indicate that Zantac enhances acetaminophen hepatotoxicity in humans." SmithKline said Tagamet is being studied as adjunctive treatment for acetaminophen overdose. The agency also said that "we have had brought to our attention" data from a double-blind, placebo-controlled study "which demonstrate that Zantac does not affect the metabolism of acetaminophen in human volunteers." The campaign was brought to FDA's attention by Glaxo. The Tagamet ad cites a letter published in Annals of Internal Medicine in support of a claim for a lower risk of hepatotoxicity than Zantac. However, the agency stated, the author of that letter "uses FDA spontaneous adverse reaction reports, which is inappropriate. Moreover, the letter ignores reports of hepatic injury associated with Tagamet in the same database." The promotions also inappropriately claim superior safety in the lack of drug interactions for patients on either theophylline or concomitant warfarin therapy, FDA said. The claim is made "in the face of explicit warnings in the Tagamet package insert that such adverse effects may occur." Glaxo has initiated a print campaign for Zantac which claims superiority over Tagamet in maintenance therapy. The claim is based on two clinical studies by Stephen Silvis, MD, chief of special diagnostic and treatment unit, V.A. Hospital, University of Minnesota, and K. R. Gough, MD, Bath Clinic, England. However, SK&F has taken the position that the studies are "statistical outliers" at variance with a substantial body of data in the literature showing that the drugs are comparable for maintenance therapy, the spokesperson maintained.