Shares of Discovery Laboratories ( DSCO) were among the worst-performing health-related stocks Wednesday, plunging 29% after the biotechnology company received a second letter from the Food and Drug Administration addressing additional conditions needed for the approval for its Surfaxin drug, used for the prevention of respiratory distress syndrome in premature infants.

The company said that the FDA is focusing on information that relates to the chemistry, manufacturing and controls section of its new drug application. "The information predominately involves the further tightening of active ingredient and drug product specifications and related controls," Discovery Labs said. The company has received two approvable letters since the company's NDA for Surfaxin was filed in April 2004. "In light of today's news, we are analyzing all aspects of our business with an intention to conserve cash while remaining focused on developing our NICU franchise of Surfaxin and Aerosurf," Discovery said. Shares were trading down $2.07 to $5.02.

St. Jude Medical ( STJ) slumped 13% after the medical device maker warned that first-quarter earnings and sales will miss its earlier guidance. The company sees earnings of 35 cents to 36 cents a share, including 3 cents a share in stock-based compensation costs, on sales of about $784 million, down from an earlier view of $799 million to $839 million. Analysts surveyed by Thomson First Call project earnings of 39 cents a share on sales of $827.5 million. Previously, the company forecast earnings of 41 cents to 43 cents a share, excluding stock-based compensation costs of 3 cents to 4 cents a share. The company said its results were hurt by lower-than-expected sales of implantable cardioverter defibrillators. St. Jude plans to release first-quarter results on April 19. Shares were trading down $5.29 to $36.01.

Shares of Affymetrix ( AFFX) rose modestly after the gene technology company agreed to license a number of patents to Abbott Molecular, a division of Abbott Labs ( ABT - Get Report). Abbott Molecular will use the patents to make comparative gene tests, related readers and software for use in the research and diagnostic fields. Financial terms of the deal were not disclosed. Affymetrix shares were trading up 17 cents to $32.28.

Millipore ( MIL) rose slightly after the bioprocess and bioscience products company said it plans to buy Newport Bio Systems, a provider of process containers used in biopharmaceutical production. "Our goal is to become the leading provider of disposable manufacturing solutions to the biopharmaceutical industry," Millipore said. "The addition of Newport Bio Systems will enable us to strengthen the breadth of our offering and bring new capabilities into our company." Millipore did not offer financial details or say when it would close the acquisition. Shares were trading up 3 cents to $73.18.

Shares of Visicu ( EICU) vaulted 48% on the company's first day of trading as a public company. The health care information technology company's initial public offering priced 6 million shares at $16 each, above the company's recently raised $13 to $15 range. Visicu plans to use proceeds from the $96 million offering to fund general needs and to support the growth of its business, the company said in a regulatory filing. Morgan Stanley led the underwriting syndicate. Shares recently advanced $7.67 to $23.67.

Other health care volume movers included Tenet Healthcare ( THC), up $1.19 to $9.09; Boston Scientific ( BSX), down 28 cents to $21.86; Medtronic ( MDT), down 76 cents to $50.64; Pfizer ( PFE), up 8 cents to $25.18; Generex Biotechnology ( GNBT), up 8 cents to $2.57; Novavax ( NVAX), up 35 cents to $6.55; Amgen ( AMGN), up 85 cents to $72.87; UnitedHealth Group ( UNH), up 17 cents to $55.47; Johnson & Johnson ( JNJ), down 20 cents to $58.62; Bristol-Myers Squibb ( BMY), up 8 cents to $24.55; Elan ( ELN), up 4 cents to $14.47; and Schering-Plough down 5 cents to $18.95.