The US Justice Department on Thursday announced its intention to join two lawsuits against a unit of Johnson & Johnson that accuse the company of marketing the heart drug Natrecor for unauthorized uses, thus defrauding Medicare and other federal health programs.

Natrecor was approved by the Food and Drug Administration in 2001 to treat severe cases of congestive failure for hospitalized patients, according to a statement of the US Justice Department. However, soon after approval, Scios, a unit of Johnson & Johnson began advertising the drug for people with less severe heart failure, a so-called off-label use not approved by the FDA.

Although doctors are free to prescribe drugs for off-label uses, companies are not allowed to promote them.

A few years ago, two analyses on Natrecor concluded that patients taking it were at increased risk of kidney problems and mortality. That’s when the drug came under scrutiny. In 2005, a panel of leading cardiologists urged J7J to stop promoting Natrecor for patients with less severe heart failure. Two years later, the company released results of a study showing no medical benefit for those patients.

The US Justice Department is joining two lawsuits filed by former Scios managers against the company and J&J. Their lawsuits were filed under a federal provision that allows people to file suits when they think the government is being defrauded.

“Medicare does not cover drugs used for off-label uses unless such off-label use is established to be medically necessary. The federal health programs -- in particular, Medicare -- paid substantial amounts for the serial outpatient off-label use,” the Justice Department said.