WASHINGTON — Americans who are badly hurt by a generic drug may not sue the drug maker for compensation, the Supreme Court ruled today, giving manufacturers a shield from liability for the medications taken most commonly in this country.

The 5-4 decision tossed out a $21 million jury verdict in favor of a New Hampshire woman who suffered horrible skin burning over most of her body and was nearly blinded after taking a pill to relieve shoulder pain.

The court majority said the federal Food and Drug Administration had approved this drug for sale and that federal approval trumps a state’s consumer-protection laws.

In the case decided today, Karen Bartlett, the woman who suffered the severe reaction to sulindac, sued Mutual Pharmaceuticals, and a jury decided the pain pill was unreasonably dangerous.

The company appealed, arguing that the verdict conflicted with federal law.

Bartlett’s “situation is tragic and evokes deep sympathy, but a straightforward application of preemption law requires that the judgment (in her favor) be reversed,” Justice Samuel A. Alito Jr. wrote for the court majority.

The ruling creates an oddity in the law. People who are hurt by a brand-name drug can sue the drug maker for damages, the Supreme Court said in 2009.

But the same is not true for those who take a generic drug. The court has now handed down two rulings that have closed the door to lawsuits from people injured by a generic drug.

About 80 percent of prescriptions written in this country are for generic drugs.