WASHINGTON — Abbott Laboratories has pleaded guilty and agreed to pay $1.5 billion over allegations that it promoted the antiseizure drug Depakote for uses that were not approved by the Food and Drug Administration.

Deputy Attorney General James Cole said today the settlement reflects the determination by government “to hold accountable those who commit fraud.”

At a news conference at the Justice Department, U.S. Attorney Timothy Heaphy said that the top levels of Abbott carried out a strategy of systematically marketing the drug for purposes other than what federal regulators had intended.

The misconduct was not the product of “some rogue sales representatives,” said Heaphy, the U.S. attorney for the western district of Virginia. The company engaged in the strategy from 1998 to at least 2006, said Heaphy.