Shares of

Emdeon

(HLTH)

were among the worst-performing health-related stocks Friday, falling 7% after the health-information company said its 2006 results may be at low end of its previous guidance. The company also announced the resignation of its president.

Emdeon said earnings and sales might be at the lower end of its previous guidance because of weakness at its business services segment. In early November, the company projected 2006 earnings $90 million and $105 million, or 24 cents to 28 cents a share, and sales of $1.36 billion to $1.41 billion. Income before taxes and other items, meanwhile, was expected to be between 58 cents and 66 cents a share. Analysts are expecting earnings of 61 cents a share on sales of $1.38 billion.

Emdeon said Tony Holcombe, president of the company and its business services segment, resigned effective Dec. 2. Holcombe is leaving the company to pursue another business opportunity, the company said. The business services segment will report to Kevin Cameron, Emdeon chief executive, until a replacement is found.

Separately, Emdeon announced a tender offer to buy up to 60 million shares at $8.20 apiece, which would represent about 17% of the company's outstanding stock. The tender offer, which will remain open for at least 20 business days, will be financed by cash on hand. Emdeon shares recently were trading down 62 cents to $7.75.

Patterson

(PDCO) - Get Report

shares plunged 17% after the distributor of pet, dental and rehabilitation supplies lowered its fiscal second-quarter and full-year projections. The company estimates earnings of 32 cents a share and revenue of $641 million for the second quarter ended Oct. 29. The company's earlier guidance called for earnings of 35 cents to 37 cents a share. Patterson said its results were hurt by weaker-than-projected sales growth of basic dental equipment and a below-plan performance at its medical unit.

The company said it is taking steps to revive the basic dental-equipment business, but those measures aren't expected to have a near-term impact on sales. As a result, Patterson reduced its full-year earnings forecast to a range of $1.44 to $1.46 a share from $1.54 to $1.58. Analysts had forecast per-share earnings of 35 cents for the second quarter and $1.53 for the full year. Patterson shares recently were down $7.32 to $34.88.

Shares of

Elan

(ELN)

and

Biogen Idec

(BIIB) - Get Report

rose Friday after the Food and Drug Administration granted priority review status for the companies' Tysabri multiple sclerosis drug. Biogen and Elan pulled the drug from the U.S. market earlier this year and suspended clinical trials after Tysabri was linked to progressive multifocal leukoencephalopathy, a potentially fatal brain disease. Results from a recent safety evaluation of 3,000 Tysabri patients didn't turn up any new confirmed cases of PML beyond the previous three cases the companies identified, Elan and Biogen said. "We are pleased that Tysabri has received priority review designation, which we believe, reflects the unmet need in MS," Biogen said. "We look forward to working with the FDA throughout the review process and are hopeful that we will be able to bring Tysabri back to people living with MS." Shares of Elan were trading up 41 cents to $10.71 while shares of Biogen rose 65 cents to $45.46.

Onyx Pharmaceuticals

(ONXX)

rose 3% after the company priced 5 million shares at $25.25 apiece in a secondary offering. The sale, announced earlier this week, is expected to close around Nov. 22. Merrill Lynch and Morgan Stanley are serving as underwriters for the offering. Onyx shares were up 78 cents to $26.16.

Other health care volume movers included

Pfizer

(PFE) - Get Report

, up 6 cents to $21.41;

Schering-Plough

( SGP), up 21 cents to $19.71;

Merck

(MRK) - Get Report

, up 56 cents to $30.17;

Johnson & Johnson

(JNJ) - Get Report

, down 49 cents to $62.52;

Amgen

(AMGN) - Get Report

, up 18 cents to $83.26;

Guidant

( GDT), down 41 cents to $62.14;

Gilead Sciences

(GILD) - Get Report

, up 10 cents to $54.85;

Bristol-Myers Squibb

(BMY) - Get Report

, up 34 cents to $22.31; and

Novavax

(NVAX) - Get Report

, down 4 cents to $3.34.