Merck & Co will pay roughly $950 million to settle criminal and civil charges that it promoted the painkiller Vioxx for an unapproved use, the U.S. Justice Department said on Tuesday.

The fine will conclude a long-running investigation into Merck's promotion of its one-time blockbuster drug, which was withdrawn from the market in September 2004 after being linked to heart risks.

The Justice Department alleged that Merck promoted the drug for treating rheumatoid arthritis before it had been approved for that condition by the U.S. Food and Drug Administration.

The case is the latest settlement by a major pharmaceutical company over marketing drugs in the United States for uses that have not been approved by the FDA, known as off-label promotion.

Merck pled guilty to a misdemeanor charge and paid $321.6 million for introducing the misbranded drug Vioxx into interstate commerce.

It also agreed to pay an additional $628.4 million civil settlement to resolve additional allegations regarding its off-label marketing of Vioxx. Merck said the settlement does not mean it admits liability or wrongdoing.

We believe that Merck acted responsibly and in good faith in connection with the conduct at issue in these civil settlement agreements, including activities concerning the safety profile of Vioxx, said Bruce Kuhlik, executive vice president and general counsel of Merck, in a statement.

The large American drugmaker had already told investors in October 2010 it was taking a $950 million charge related to the previously disclosed U.S. government probe.

The civil settlement agreement is signed with the United States and individually with 43 states and the District of Columbia, but previously disclosed litigation with seven states is still unresolved, Merck said.

In 2007, Merck also agreed to pay $4.85 billion to settle lawsuits filed by former Vioxx users, who alleged they had been harmed by the pill.

(Reporting by Sarah N. Lynch and Anna Yukhananov; Editing by Tim Dobbyn and Carol Bishopric)