Thousands of federal lawsuits claiming the drug Vioxx caused heart attacks and other conditions that killed or injured people cannot be pooled into one national class action, a judge ruled Wednesday.

U.S. District Court Judge Eldon Fallon, who was appointed to deal with pretrial matters for all federal suits involving Merck & Co.'s (MRK) withdrawn painkiller, did not rule on the possibility of separate class-actions suits for each state and the District of Columbia.

Click here to see the judge's ruling. (FindLaw)

His 25-page ruling rejected the plaintiffs' proposal to try all of the cases under the laws in New Jersey. They argued that the company should reasonably expect to follow the laws of the state where it is headquartered.

"While this is true, it is just as true that Merck, an international corporation providing its drugs to every state in the nation, should expect to abide by every jurisdiction's laws," Fallon wrote.

Since plaintiffs in other states couldn't reasonably expect their personal injury claims to be governed by New Jersey law, it makes more sense to apply the law of each plaintiff's home state to that plaintiff's claims, Fallon ruled.

"Each plaintiff's home jurisdiction has a stronger interest in deterring foreign corporations from personally injuring its citizens and ensuring that its citizens are compensated than New Jersey does in deterring its corporate citizens' wrongdoing," he wrote.

Fallon wrote he was "confident that common questions exist" in the 7,000-plus lawsuits — something required for class actions.

But, he said, allegations that Merck failed to warn doctors adequately about the drug's alleged health risk, "necessarily turn on numerous individualized issues."

He wrote these issues include "the alleged injury; what Merck knew about the risks of the alleged injury when the patient was prescribed Vioxx; what Merck told physicians and consumers about those risks in the Vioxx label and other media, what the plaintiffs' physicians knew about the risks from other sources, and whether the plaintiffs' physicians would still have prescribed Vioxx had stronger warnings been given."

Merck has vowed to fight each Vioxx case individually. Its shares rose 30 cents to $44.52 in afternoon trading on the New York Stock Exchange.