Merck & Co., the second-largest U.S. drugmaker, received a subpoena from the Department of Justice related to the sales of cancer and antiviral drugs.

The U.S. department asked for details of the marketing and selling of Temodar, PegIntron and Intron A, from January 1, 2004 to the present “in a federal health-care investigation,” Merck said today in a filing.

“This is the first disclosure of this matter,” Ronald Rogers, a spokesman for Whitehouse Station, New Jersey-based Merck, said in an e-mail. The drugmaker is cooperating with the investigation, Rogers said, declining to provide additional information.

Temodar, used to treat brain cancer, accounted for $1.07 billion in sales last year. Intron A for cancer and PegIntron for hepatitis C together generated $946 million in sales.

Merck dropped $1.77 cents, or 5.6 percent, to $29.94 at 4:00 p.m. in New York Stock Exchange composite trading, the lowest price since August 2009. The shares have declined 17 percent this year.

source:Merck & Co.,