In a decision handed down late last week, the US Supreme Court gave manufacturers of generic drugs significant legal protection from liability. In Pliva v. Mensing, the Court ruled that patients cannot sue these companies under state law for failing to warn them about the risks associated with their drugs. Although generic-drug firms may welcome the decision, I think it has unpalatable implications.

The case began after several patients took a generic version of metoclopramide for stomach ailments and ultimately developed tardive dyskinesia, a serious neurological disease. As required under federal law, the label for the generic product was the same as that for the branded drug, which was no longer available. But the plaintiffs alleged that the manufacturer of the generic drug had evidence about the product’s potential side effects and failed to alert FDA about them as state law required.

In his majority opinion, Justice Thomas ruled that federal law pre-empts the plaintiffs’ suit. A company cannot comply both with federal law, which requires manufacturers to use the same warning label as that for the branded product, and with a state law that requires them to change the warning label when evidence supports it, he held. In such an instance, federal law prevails over state law. Yet Thomas conceded that if the generic-drug manufacturers had asked FDA for help in changing the corresponding brand-name label, they might have been able to accomplish under federal law what state law required.

In her dissent, Justice Sotomayor wrote that FDA requires generic-drug firms to propose label changes when they believe that a label is inadequate. But the defendants (Actavis and Pliva) made no such proposals. Generic-drug manufacturers might sometimes be able to prove that it would be impossible for them to comply with federal and state laws regarding labeling, wrote Sotomayor. But the defendants showed “only that they might have been unable to comply with both federal law and their state-law duties to warn” the plaintiffs about side effects [emphasis mine].

“As a result of today’s decision, whether a consumer harmed by inadequate warnings can obtain relief turns solely on the happenstance of whether her pharmacist filled her prescription with a brand-name or generic drug,” wrote Sotomayor. Given that more and more prescriptions are being filled with generic drugs, this conclusion is distinctly troubling.

In light of the Court’s decision, we may need to re-evaluate the process for changing drug labels to ensure that it is sound and reasoned without being onerous. Most importantly, we need to protect patients’ right to seek redress if any manufacturer has failed in its obligation to provide adequate warnings about potential side effects.