Antihistamine drug wars: Claritin vs Zyrtec

Healthfacts, June, 1996 by Arthur A. Levin

Once again, fierce competition for doctor and consumer loyalty to a brand-name drug (not to mention almost $2 billion in U.S. sales) between drug manufacturers has spilled over into court. Although the lawsuits were settled before trial, the battle for the hearts and minds of 50 million allergy sufferers continues to be fought in print and on TV between Schering-Plough, makers of the best-selling antihistamine Claritin, and Pfizer whose new antihistamine, Zyrtec, was approved in December 1995.

First sold in 1992, Claritin has been heavily marketed directly to consumers and accounts for half of all antihistamines sold in the U.S. Its success has come mainly at the expense of two former best-selling non-sedating antihistamines, Seldane and Hismanal. Their sales have plummeted in the past two years because of reports of life-threatening interactions with certain antibiotics (erythromycin) and antifungal medications (ketoconazole).

Schering-Plough's suit against Pfizer alleges that Zyrtec was marketed to doctors as non-sedating when, in fact, the drug does not meet the FDA standard for making such a claim. In the studies required by the FDA prior to approval, researchers found that 14% of people taking Zyrtec reported being sedated, compared to only 6% of people taking a placebo (inactive) control. Zyrtec's drug label is required to contain a precautionary warning about sedation. Pre- approval studies of Claritin found it was no more sedating than a placebo and as a result the FDA classified the drug as non- sedating. Pfizer's counter-suit alleges that Schering-Plough management had engaged in a wide-ranging strategy to exaggerate the incidence of sedation with Zyrtec (Scrip, 22 March 1996).

In an effort to exploit the fact that Claritin is classified as non-sedating, Schering-Plough has linked up with a non-profit group called Citizens Against Drug Impaired Drivers (CANDID). This spring CANDID, which was founded by parents of a child killed by a drug- impaired driver, ran print ads and mailed letters to hundreds of thousands of doctors warning of the dangers of mixing driving and sedating drugs. Although Schering-Plough designed, carried out, and paid for these campaigns, there was no attribution of their sponsorship. Schering defends the relationship by pointing out that their involvement with CANDID predates the launch of Zyrtec.

RxNews has three comments. First, the approval of Zyrtec suggests that the FDA's power to approve or disapprove new drugs may actually be too limited, rather than too restrictive, as its critics in Congress and the public assert. Ideally, Zyrtec should not have been approved at all because it is less safe than an already marketed drug. Second, this is but one more example of how tens of millions of dollars spent on marketing to doctors and directly to consumers can obfuscate any concerns about a new drug's comparative safety. Third, even though CANDID's message may be genuinely in the public interest, the organization's failure to attribute sponsorship to Schering-Plough is one more example of a disturbing trend the willingness of not for profit organizations to accept under the table drug company support for programs that directly help the contributor's sales.