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 New Orleans federal judge has ruled.

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Court Judge Eldon Fallon, who was appointed to deal with pretrial matters for all federal suits involving Merck & Co.’s withdrawn painkiller, did not rule on the possibility of separate class action suits for each state and the District of Columbia.