Shares of Questcor Pharmaceuticals Inc. plummeted today after a website said that it will publish a negative report on the Anaheim drug maker.

Investors sent Questcor’s stock down about 15% today to a market value of $2.2 billion.

Questcor makes H.P. Acthar Gel, which is used to treat various conditions, including multiple sclerosis flare-ups, the kidney disorder nephrotic syndrome and infantile spasms, a very rare form of epilepsy.

Website told its members in an email that “the first story in a detailed two-part series on Questcor Pharmaceuticals will be released early next week, with the second installment scheduled to appear soon after that,” according to said the first article “raises serious questions about the aggressive marketing practices of the company,” while the second story will focus on business practices and have a “hard look” at Questcor’s leaders, said.

Questcor said in a statement that it became aware that an investor blog is preparing to issue a report regarding (its) marketing and business practices, and it "believes that its marketing and business practices are consistent with regulatory requirements and industry standard practices."

Questcor will speak to to discuss the company and its marketing and business practices, it said. said that it has sold 80,599 shares of Questcor short at an average price of $41.46 a share.

It has criticized other Orange County companies, most notably, an Irvine operator of a search engine to find local businesses, in 2010.