The Supreme Court ruled Monday that makers of generic drugs cannot be sued under state law for adverse reactions to their products, a decision that consumer advocates called a blow to patient safety.

In a 5 to 4 vote, the court ruled for Mutual Pharmaceutical, overturning a multimillion-dollar jury award to a badly injured patient in New Hampshire who alleged a generic drug she had taken was unsafe based on its chemical design. Mutual is owned by Sun Pharmaceutical Industries.

The majority opinion, written by Justice Samuel A. Alito Jr., said the state’s law could not run against federal laws regarding prescription medicines whose design has been approved by the Food and Drug Administration.

A Supreme Court ruling in 2011 found that pharmaceutical companies that make branded drugs are liable for inadequacies in safety warnings on a medicine’s label but that the makers of cheaper copies of those medicines are not.

The consumer watchdog group Public Citizen said the Supreme Court decision Monday undermines patient safety at a time when about 80 percent of U.S. prescriptions are filled with generic medicines.

“Today’s court decision provides a disincentive for generic makers of drugs to monitor safety of their products and to make sure that they have a surveillance system in place to detect adverse events that pose a threat to patients,” Michael Carome, director of Public Citizen’s Health Research Group, said in an interview.

He pointed out that, in many cases, the potentially dangerous side effects of medicines have not come to light until decades after they were approved and often after there was no longer a branded version on the market.

With the threat of litigation removed, “groups that think this undermines patient safety could be onto something,” said David Maris, an industry analyst with BMO Capital Markets. “The blanket protection that they are under now is that if the FDA says you are approved, as long as [generic-drug makers] don’t introduce new problems into the drug, then they’re fine.”

Mutual Pharmaceutical had asked the court to overturn a $21 million jury award to Karen Bartlett, a New Hampshire woman who took Mutual’s generic nonsteroidal anti-inflammatory drug, sulindac, in 2004 after her doctor prescribed it for shoulder pain. Sulindac is a generic version of Merck’s Clinoril.

Bartlett suffered a rare hypersensitivity reaction three weeks after she started taking it. Her skin began to peel off, leaving her severely disfigured, with burnlike lesions over two-thirds of her body, and nearly blind.

Mutual, backed by the Obama administration, said federal law trumped state-law claims such as those Bartlett had made, pointing to the fact that the drug had already won FDA approval with an agency-approved label carrying safety warnings.

Federal law requires generic drugs to have the same design and warning labels as their brand-name equivalents, Mutual argued.

The high court agreed.

— Reuters