Issues Remain for Warfarin

Chain Drug Review, Jan 18, 1999

NEW YORK -- A federal judge in Wilmington, Del., dismissed a claim by Barr Laboratories Inc. that DuPont Pharmaceuticals violated federal antitrust law in advocating before state legislatures patients' right to know which kind of warfarin, an anticoagulant medication, they have been prescribed.

But in Virginia the state pharmacy board has refused to promulgate regulations restricting the substitution of Narrow Therapeutic Index (NTI) drugs, including warfarin sodium. The Virginia Board of Pharmacy accepted the recommendation of its regulation subcommittee to continue to allow consumers to have access to equivalent, more affordable generic medicines, according to Barr chairman, president and chief executive officer Bruce Downey.

In a related pretrial ruling in the Delaware case Judge Sue Robinson dismissed three consolidated consumer class-action suits alleging DuPont Pharmaceuticals monopolized the anticoagulation market with its drug Coumadin (warfarin sodium tablets, USP).

"Since it launched its product in August 1997 Barr has engaged in a state-by-state effort to prevent physicians from knowing their patients are receiving Barr's generic warfarin," says Nicholas Teti, president of DuPont Pharmaceuticals. "The court has recognized that DuPont has the right to seek legislation to ensure that the almost 3 million elderly Americans who are being treated with Coumadin have the right to know whether their medication is being switched without their approval."

DuPont has contended that generic formulations of drugs with an NTI should have a more rigorous standard of approval and that patients who take these drugs and their physicians should be informed when they are switched from one brand of these medications to another.

An NTI drug is one whose dosage must be carefully administered and monitored because there is very little difference in what makes an effective dose and what could be a toxic dose.

Barr makes a generic version of Coumadin, which is prescribed for patients to prevent stroke and other complications associated with such events as atrial fibrillation, heart valve implantation and deep-vein thrombosis. The most common adverse occurrence and serious risk of oral anticoagulation therapy with Coumadin is bleeding in any tissue or organ.

The court said the plaintiffs had no direct relationship with DuPont because they "purchased Coumadin from intermediaries" rather than from the branded manufacturer.

Although certain of Barr's claims were not dismissed, DuPont officials expressed confidence that the company will prevail against these other claims as well.

But Downey described the Virginia decision as a victory for consumers in that state.

"The [Virginia] pharmacy board has repeatedly determined that it is not necessary to restrict generic substitution," he said in the aftermath of that ruling.

"The decision is supported by clinical science as well as the repeated statements by the Food and Drug Administration that AB-rated generic medicines offer patients, pharmacists and physicians the same safety and efficacy as the equivalent brand product."

Together, Barr's warfarin sodium and Coumadin are the nation's 11th most refilled prescription drug in the United States, with over 19 million prescriptions written in the last 12 months. Barr markets warfarin sodium in all nine strengths.