Nine years ago, Diana Levine lost her lower arm to gangrene after a botched injection of the Wyeth drug Phenergan.

Yesterday, she won a victory before the U.S. Supreme Court, which ruled that Wyeth must pay for her loss in a decision that upheld the importance of consumers' right to sue drug companies over injuries.

It was, Levine said, a victory for "the little guy."

In a 6-3 opinion written by Justice John Paul Stevens, the court said consumer lawsuits "uncover unknown drug hazards and provide incentives for drug manufacturers to disclose safety risks promptly."

The case had been billed as the most important business decision in several years because it is likely to affect consumer litigation against many industries.

Wyeth, which is based in Madison, N.J., and has pharmaceutical headquarters in Collegeville, had argued that it should not be subject to such suits because the U.S. Food and Drug Administration already had approved the Phenergan label. That label contained warnings about the risk of gangrene and amputation when Phenergan was delivered through an intravenous method known as IV push.

Levine, a 63-year-old Vermont musician, argued that Wyeth should have gone further and forbidden administering the drug through an IV push, but Wyeth said it could not make that change unless the FDA directed it to do so.

The court's majority opinion called Wyeth's argument "meritless." Stevens wrote that the court found no evidence that Wyeth had tried to strengthen the warning or that the FDA had disallowed stronger language.

Plaintiffs' attorneys and consumer groups hailed the ruling, which upholds a lower court's $6.7 million award to Levine. The pharmaceutical industry and pro-business groups criticized it for giving state juries authority over regulatory matters better left to experts at the FDA.

"I'm a happy man," said Sol Weiss, a Philadelphia plaintiffs' lawyer. "This doesn't mean you're going to win, but you get your day in court."

While not involved in this case, he is hoping that the decision will revive his cases involving Pfizer Inc.'s antidepressant Zoloft and GlaxoSmithKline P.L.C.'s antianxiety agent Paxil.

He and others had worried that a ruling for Wyeth would have prevented lawsuits that have highlighted risks of various drugs, including Merck & Co. Inc.'s pain reliever Vioxx.

"Under this ruling, an injured person can still get justice," said Ed Blizzard, a prominent plaintiffs' lawyer who is suing AstraZeneca P.L.C. over injuries his clients blame on the antipsychotic drug Seroquel.

Fred Magaziner, a partner with Dechert L.L.P., has represented many drug companies, although not Wyeth in this case. He said the decision gave juries too much power to second-guess the FDA.

"This is disappointing to pharmaceutical companies because the majority opinion does not seem to take into account the tension between what companies are required to do by the FDA and what juries in particular cases, sometimes involving tragic injuries, believe that the companies should have done," he said. "The FDA can take into account medical and scientific considerations that apply to all users of the drug that a single jury is just not able to weigh when deciding the case of a particular individual," Magaziner said.

Levine's case involved a legal principle known as preemption: whether FDA decisions preempt, or override, state law. For decades, FDA officials had viewed state law as a "complementary form of drug regulation," Stevens wrote.

But in 2006, FDA chief counsel Dan Troy challenged that view, arguing that FDA decisions preempted state claims. Troy, now a lawyer representing GlaxoSmithKline, was not available for comment. His promotion of preemption was part of an overall Bush administration approach to business regulation.

Stevens said the FDA's turnabout was "inherently suspect" because the agency had given interested parties no chance to comment on the change.

Wyeth attorney Bert Rein maintained that the company had done nothing wrong in the Levine case.

Although Levine pointed to 20 cases of injury involving Phenergan administered through an IV push over several decades, Rein said the FDA was aware of those cases and had not demanded a label change. The company had retained IV push as a delivery method because some doctors thought it helped patients who needed immediate relief from nausea.

"Wyeth fully complied with federal law in its labeling of Phenergan, which provided clear instructions and warnings about its use," he said.

Chief Justice John G. Roberts Jr. and Justices Antonin Scalia and Samuel Alito agreed with Wyeth and wrote a dissenting opinion.

"This case illustrates that tragic facts make bad law," Alito wrote in the dissent. "The court holds that a state tort jury, rather than the FDA, is ultimately responsible for regulating warning labels for prescription drugs."

Levine, speaking by phone from her Vermont home, could barely breathe shortly after hearing the news from an Associated Press reporter.

"I'm just overwhelmed with gratitude and surprise," she said.

In spring 2000, she went to a local clinic to have her migraine headache treated. A physician's assistant gave her Demerol for pain and, via IV push, Phenergan for nausea. The physician's assistant apparently missed Levine's vein and hit an artery, causing gangrene that led to the amputation of her lower arm several weeks later.

She said the money would compensate for lost wages and help her pay for a garage, something she never felt she needed until she lost her hand. Now, she said, scraping piles of snow off her car is much more difficult. She also will retrofit her car to make it easier to drive with one hand.

"I feel like today's decision is going to protect many people," she said. "The little guy won."

Read the justices' opinions at http://go.philly.