Shares of

Tenet Healthcare

(THC) - Get Report

dipped 1.8% Thursday after the company reached a $900 million settlement with the Justice Department related to its alleged over-billing of Medicare.

Tenet agreed to pay $725 million to settle federal investigations into its transactions with the federal health insurance program before 2003, and will waive its right to pursue $175 million in past Medicare payments.

While the company did acknowledge that it "made mistakes in its conduct before 2003," the settlement means investigations will cease and no conclusion will be reached on whether Tenet broke the law. Shares of Tenet fell 13 cents to $7.11.

Pharmaceuticals giant

Pfizer

(PFE) - Get Report

plans to introduce its own generic version of its branded antidepressant Zoloft. Shares of Pfizer gained 34 cents, or 1.5%, to $23.24.

Generic-drug maker

Teva Pharmaceutical

(TEVA) - Get Report

, which received Food and Drug Administration approval to market a generic version of Zoloft, fell $1.05, or 3.3%, to $31.29.

The company had already been dealing with

Merck's

(MRK) - Get Report

decision to undercut Teva with its own generic version of the cholesterol drug Zocor and an ongoing patent infringement battle with

Abbott

(ABT) - Get Report

over a generic version of the antibiotic Biaxin.

Bristol-Myers Squibb

(BMY) - Get Report

was up 1.8% following the company's announcement Wednesday that it received Food and Drug Administration approval to market its new drug Sprycel for a blood cancer known as Philadelphia chromosome-positive acute lymphoblastic leukemia in patients who did not adequately respond or could not tolerate other treatments. Bristol says the drug should be available for sale nationwide within days.

The FDA also granted Sprycel accelerated approval for the treatment of adults with the blood disease chronic myeloid leukemia with resistance or intolerance to prior therapy, including

Novartis'

(NVS) - Get Report

blockbuster drug Gleevec. Accelerated approval allows a company to submit its application for a drug's approval on a rolling basis instead of the traditional method of submitting it all at once. Bristol shares traded up 46 cents to $25.70.

Biogen Idec

(BIIB) - Get Report

and

Elan

(ELN)

received European approval to market the multiple sclerosis drug Tysabri. The drug recently returned to the U.S. market after concerns about a link to a potentially deadly brain disease led to its withdrawal. Biogen shares rose 4.4% to $46.97, while Elan was up 1% to $16.49.

Shares of cancer drug developer

Adventrx

(ANX)

spiked when the company released promising preliminary phase II data for its proposed drug for metastatic colorectal cancer, but sank 12.6% later in the day to close at $3.41.

According to data from the mid-stage trial in patients receiving chemotherapy with or without the cancer drug CoFactor, the median survival time for those receiving the drug was extended by two months compared with those on chemotherapy alone. Results were reported at the World Congress on Gastrointestinal Cancer meeting in Barcelona, Spain.

Drug developer

Keryx Biopharmaceuticals

(KERX) - Get Report

also announced positive phase II results Thursday. Final analysis of a dosing study for its proposed kidney cancer drug Zerenex found that the drug was safe and well tolerated at three dosage levels. Keryx shares were up 8% to $13.65.

Diagnostics-device maker

Abaxis

(ABAX) - Get Report

were boosted when the maker of blood-analyzing devices announced a marketing deal with

Henry Schein

(HSIC) - Get Report

, a provider of health care products and services to medical offices in North American and Europe. Shares were up 7.3% to $22.