Shares of American Pharmaceutical Partners ( APPX) were among the worst-performing health-related stocks Monday, plunging 16% after the company said it plans to buy privately held American BioScience, its parent company, in a stock deal initially valued at about $4.1 billion.

The new company, which expects more than $500 million in sales during 2005, will be called Abraxis BioScience. As part of the deal, American Pharmaceutical will issue 86 million shares. American BioScience, which currently owns about 64% of the company, will own almost 84% of the combined company after the deal. The merger is expected to close during the first half of 2006. Shares of American Pharmaceutical Partners recently were trading down $7.72 to $39.89.

Henry Schein ( HSIC) fell 1% after the hospital supply company backed its 2005 earnings guidance and projected 2006 earnings in line with Wall Street's forecast. The company continues to expect 2005 earnings of $1.77 to $1.83 a share. Analysts polled by Thomson First Call have an average estimate for earnings of $1.81 a share.

For 2006, Henry Schein expects earnings, excluding items, of $2.20 to $2.26 a share, bracketing the $2.22 a share that analysts had forecast. "Our 2006 diluted EPS guidance is in line with our long-term corporate goals of high-single digit internal sales growth and 30-50 basis points of operating margin expansion," the company said. "Of course, sales growth and margin expansion for 2006 will be enhanced by the expected increase in influenza vaccine sales compared with 2005. This translates into 26% growth in diluted earnings per share compared with 2005." Shares were down 52 cents to $42.75.

Shares of Merck ( MRK) fell 4% after the drug company laid out plans to cut 7,000 jobs and close or sell five of its 31 manufacturing plants over the next three years. Merck expects the initial phase of its cost-reduction plan to result in pretax savings of $3.5 billion to $4 billion from 2006 to 2010. "The actions we are announcing today are an important first step in positioning Merck to meet the challenges the company faces now and in the future," the company said. The job cuts represent about 11% of the company's workforce.

Merck expects 2005 earnings, before items, of $2.47 to $2.51 a share. The company forecast 2006 earnings, before restructuring charges but including 7 cents a share related to stock option expensing, of $2.28 to $2.36 a share. Analysts expect 2005 earnings of $2.50 a share and 2006 earnings of $2.39 a share. Merck shares fell $1.13 to $29.85.

Delcath Systems ( DCTH) fell 7% after the medical device maker completed a $2.5 million private placement. The company sold about 753,000 shares and issued warrants to purchase about 188,000 shares. "The company has undertaken the sale of these securities to put itself in a better position to pursue the pending clinical trials of the Delcath system, including the possible expansion of the trials to additional sites," it said. Shares were down 25 cents to $3.30.

Other health care volume movers included Pfizer ( PFE), up 7 cents to $21.74; Johnson & Johnson ( JNJ), up 25 cents to $62.40; Bristol-Myers Squibb ( BMY), down 17 cents to $22.09; Emdeon ( HLTH), down 13 cents to $7.55; Amgen ( AMGN), down $1.43 to $81.36; Teva Pharmaceutical Industries ( TEVA), down 66 cents to $41.35; Schering-Plough ( SGP), down 1 cent to $19.55; Gilead Sciences ( GILD), down $1.90 to $52.33; and Novavax ( NVAX), down 10 cents to $3.