AstraZeneca has completed a deal to pay $520 million to settle federal investigations into marketing practices for its blockbuster schizophrenia drug, Seroquel, the Attorney General, Eric Holder, said at a news conference Tuesday afternoon.

“AstraZeneca paid kickbacks to doctors as part of an illegal scheme to market drugs for unapproved uses,” Kathleen Sebelius, secretary of health and human services, said at the event in Washington. She said the company promoted drugs for unapproved uses by children, the elderly, veterans and prisoners.

Glenn Engelmann, AstraZeneca’s U.S. general counsel, released a statement saying the company denies the allegations but settled the investigation with the payment.

“It is in the best interest of AstraZeneca to resolve these matters and to move forward with our business of discovering and developing important, life-changing medicines — while avoiding the delay, uncertainty, and expense of protracted litigation,” Mr. Engelmann said.