The US federal government has announced its backing for drugmaker Wyeth in a case to be heard by the Supreme Court which is forecast to be the most important US legal event for the pharmaceutical industry this year.

The case concerns a $6.8 million award granted by a jury in Vermont to Diana Levine, who developed gangrene and lost a hand and forearm after inadvertently being injected in an artery with the company’s antinausea drug Phenergan (promethazine). Phenergan’s labelling warned of the risk of gangrene if the drug was injected into an artery, but Ms Levine claimed that the labelling was unsafe. Her award was upheld on appeal by the Vermont Supreme Court.

However, the Food and Drug Administration (FDA) has determined Phenergan to be safe and effective and has mandated the warnings which should appear on its labelling, says Wyeth, which is urging the Supreme Court judges to rule that federal law pre-empts product liability cases brought under state laws which challenge the adequacy of FDA-approved label warnings.

The government’s amicus curiae (friend of the court) brief, which was filed by the Department of Justice, argues that Ms Levine’s claims are pre-empted by federal law because they challenge labelling which was approved by the FDA after it was informed of the relevant risk.

Another amicus brief, filed jointly by the Pharmaceutical Research and Manufacturers of America (PhRMA) and Biotechnology Industry Organization (BIO), points out that “state law cannot require what federal law prohibits.” It also warns that allowing the Vermont judgement to stand would “encourage pharmaceutical companies to inundate FDA with requests for labelling changes to ensure that federal regulators have been presented with every potential labeling permutation. These requests, driven by the need to create a record for future litigation rather than science, will distract agency scientists from their core mission of reviewing the safety and effectiveness of prescription medications.”

A joint filing by the Washington Legal Foundation (WLF) and the American College of Emergency Physicians (ACEP) argues that suits brought under state laws must be pre-empted by federal law “because they stand as an obstacle to the accomplishment of the goals of Congress and FDA.”

If the Vermont judgement were upheld, Wyeth would be required to include new safety warnings on Phenergan’s label beyond those mandated by the FDA, but if these new warnings discouraged use of the product, health care would suffer because patients would be steered away from a treatment option that FDA has deemed safe and effective, say the WLF and ACEP. Their brief includes examples of how such “overwarning” has led many patients to forgo treatment that they should be receiving and warns: “the adverse health effects of underutilisation of available drugs far exceeds the adverse health effects of from use of FDA-approved drugs.”

PhRMA senior vice president Ken Johnson emphasises that federal preemption “is not about providing blanket immunity for America’s pharmaceutical research companies” - state judges and juries can still levy damages against manufacturers which fail to comply with FDA standards, he says.

Patients are best protected by “a single, strong, uniform regulatory authority that is the sole arbiter of the benefits and risks of medicines,” said Mr Johnson, and he warned that current efforts to strengthen the FDA should not be diluted by substituting the opinions of lawyers and juries for the expert judgment of FDA scientists and doctors. “Allowing prescription medicine labels to become clogged with inconsistent warnings would confuse physicians and frighten away patients from taking life-saving and life-enhancing medicines. That would harm, not help, public health,” he said.

The Supreme Court will hear the case of Wyeth vs Levine later this year, and is also scheduled to consider other pre-emption cases involving Pfizer and medical technology company Medtronic.

Wyeth no longer markets the injectable version of Phenergan.