Updated from 1:39 p.m. EDT

Shares of Ciphergen Biosystems ( CIPH) were easily among the worst-performing health care and pharmaceutical stocks Thursday after the company warned that its second-quarter sales results would fall well short of expectations.

Citing weaker-than-expected ProteinChip system placements and a year-over-year sales decline in BioSepra sorbent, the company said that it expects second-quarter sales of about $10 million to $11 million. Analysts polled by Thomson First Call had expected second-quarter sales of $17.4 million. Shares of Ciphergen Biosystems traded down $2.93, or 40%, to $4.39.

Inveresk Research ( IRGI) rose after the company agreed to be acquired by Charles River Laboratories ( CRL) for about $1.5 billion in cash and stock. Each Inveresk share will be exchanged for 0.48 shares of Charles River and $15.15 in cash, valuing the deal at about $38.61 a share. The transaction is expected to close during the fourth quarter. Shares of Inveresk Research traded up $4.35, or 14.1%, to $35.19.

Shares of Zonagen ( ZONA) rose after the company announced that it achieved statistically significant results for its testosterone-enhancing Androxal product vs. a placebo in its phase I/II trials. Androxal, which is used to stimulate the production of testosterone by the testes, showed no side effects, and all three dose levels showed significant changes in testosterone from baseline testosterone levels. The company expects to meet with the Food and Drug Administration this summer for an end-of-study meeting. Shares of Zonagen traded up $1.98, or 77.3%, to $4.54.

WellCare Group ( WCG) performed strongly on its first day of trading as a public company. The managed care provider sold 7.33 million shares at $17 apiece, the high end of its $14 to $16 range, raising about $125 million. Morgan Stanley, SG Cowen, UBS Investment Bank and Wachovia Securities led the underwriting syndicate. Shares of WellCare Group traded up $2.53, or 14.9%, to $19.53.

Shares of Cardinal Health ( CAH) plunged after the company warned that fourth-quarter earnings would fall short of expectations and that it received a Securities and Exchange Commission subpoena pertaining to a previously announced accounting investigation. Cardinal is now expecting to earn 93 cents to 95 cents a share.

Analysts, meanwhile, had expected it to earn $1.03 a share during the fourth quarter. As for the subpoena, the SEC asked Cardinal to produce documentation relating to revenue classification and methods used for such classification in its pharmaceutical distribution business. Shares of Cardinal Health traded down $17.19, or 24.5%, to $52.86.

Health care volume movers included Pfizer ( PFE), down 35 cents to $33.93; Amgen ( AMGN), up 19 cents to $54.76; Johnson & Johnson ( JNJ), down 23 cents to $55.47; Schering-Plough ( SGP), down 40 cents to $18.08; and Genentech ( DNA), down 60 cents to $55.60.