Shares of

Anadys Pharmaceuticals

( ANDS) were among the worst-performing health-related stocks Monday, plunging 48% after the drugmaker suspended dosing of its hepatitis C treatment.

The company said it is suspending dosing in patients "pending analysis of recently obtained information from preclinical 13-week toxicology studies in animals." The company, which is developing the treatment with

Novartis

(NVS) - Get Report

, said that even though it hasn't seen any serious adverse events in its phase 1b clinical trial, it makes sense to suspend its current trial and analyze the recently obtained data.

"We will work to determine the best path forward in future development, including dose-finding activities and potential modifications of clinical trial design," Anadys said. Shares of Anadys were recently trading down $3.19 to $3.50.

Prestige Brands Holdings

(PBH) - Get Report

slumped 17% after the marketer and distributor of over-the-counter drugs and personal care products announced the resignation of its chief executive. Frank Palantoni, whose resignation is effective immediately, is leaving the company after serving less than three months as CEO.

Chairman Peter Mann, who had served as CEO until April 1 of this year, will assume the CEO position on an interim basis until a permanent replacement is found. A permanent replacement is expected within the next six months. Shares were trading down $1.67 to $8.45.

Shares of

LifePoint Hospitals

(LPNT)

fell 3% after the company named William F. Carpenter III as its new president and chief executive, effective immediately. Carpenter will replace Kenneth Donahey, who resigned after some five years as CEO. Carpenter has been with LifePoint since its inception in 1999 and most recently served as executive vice president, general counsel and secretary, chief development officer and corporate governance officer.

"My priority as chief executive officer will be to continue LifePoint's long-standing focus on being a great operating company," Carpenter said in a press release. Shares were trading down 90 cents to $31.57.

Neurocrine Biosciences

(NBIX) - Get Report

moved higher Monday. Shares in the company plunged Friday after the company said that

Pfizer

(PFE) - Get Report

pulled the plug on its partnership to develop the insomnia drug Indiplon. Neurocrine, which now plans to seek approval for the drug on its own, said that Pfizer will support Indiplon for the next 180 days during a transition period. Shares, which lost 29% of their value on Friday, were recently trading up 84 cents, or 9%, to $10.69.

Auxilium Pharmaceuticals

(AUXL)

dropped following the announcement that Gerri Henwood will resign on July 17 as chief executive, interim president and a board member pursue other opportunities. She will continue to work with the company as a consultant.

The pharmaceutical company named Armando Anido CEO and president and said he will also become a director. Anido previously served as executive vice president, sales and marketing, at

MedImmune

( MEDI). Shares of Auxilium were losing 51 cents, or 6%, to $7.99.

Other health care volume movers included

Boston Scientific

(BSX) - Get Report

, down $1.36 to $16.90;

Pfizer

(PFE) - Get Report

, up 47 cents to $23.11;

Johnson & Johnson

(JNJ) - Get Report

, down $1.44 to $59.88;

Zimmer Holdings

(ZMH)

, down $4.73 to $58.30.

Biomet

( BMET), down $1.52 to $33.46;

Merck

(MRK) - Get Report

, up 19 cents to $35.13;

Bristol-Myers Squibb

(BMY) - Get Report

, up 18 cents to $25.69;

Teva Pharmaceutical Industries

(TEVA) - Get Report

, up 9 cents to $32.28; and

Amgen

(AMGN) - Get Report

, down 26 cents to $64.67.