Mylan Inc. tumbled 8 percent yesterday after the Cecil generic drug maker posted a $443.9 million first-quarter loss, dimmed its earnings outlook and said it would realize fewer efficiencies from its $6.8 billion acquisition of Merck Generics.

Shares finished at $11.42, down $1.04. More than 35 million shares changed hands, four times the average daily volume.

The loss, which amounted to $1.46 per diluted share, was announced after the market closed Thursday. Excluding more than $500 million in one-time charges, Mylan earned 9 cents per share for the quarter, in line with estimates.

In an analyst call Thursday, Mylan executives cited two reasons they expect to earn less through 2010 than previously anticipated: the possible sale of the Dey specialty pharmaceutical business acquired in October as part of Merck Generics and higher expenses related to integrating Merck Generics, a company twice Mylan's size.

Mylan's revised forecast calls for 2008 earnings of 40 cents to 50 cents per share, down from the 70 cents to 90 cents per share it forecast in October. The numbers exclude the kind of one-time charges that put a huge dent in Mylan's first quarter results.

"The bottom line is that we have our arms around this business. The pieces are in place. We're positioned for excellent future growth," Vice Chairman and Chief Executive Officer Robert J. Coury told analysts on the call.

Mylan said it expected to realize $272 million in synergies from the acquisition by the end of 2010, down from the $317 million estimate it gave investors in October.

Yesterday's decline mirrored the stock's behavior Feb. 29, when Mylan shares slid 9 percent after the company reported a $1.4 billion loss for the fourth quarter.

Mylan shares are off 19 percent this year and have lost half of their value since the Merck Generics acquisition was announced last May.