Updated from 2:13 p.m. EST

Shares of

Aceto

(ACET)

were among the worst-performing health-related stocks Friday, falling 19.3% after the company warned that second-quarter earnings would fall short of expectations.

The pharmaceuticals distributor now expects earnings of 10 cents a share, which is below the 12 cents to 15 cents a share that it had previously forecast. Analysts polled by Thomson First Call had been expecting earnings of 14 cents a share. The shortfall, according to the company, is due to competitive pricing on certain chemical-based pharmaceutical ingredients, tight production demand in China, costs associated with the company's new business initiatives and an unexpected bad debt expense. Full results will be issued on Feb. 3. Shares traded down $2.27 to $9.49.

Beckman Coulter

( BEC) fell 6.7% after the maker of medical-testing devices posted fourth-quarter earnings that were lower than expected. The company earned $59.8 million, or 91 cents a share, on sales of $693 million. Analysts were expecting earnings of 98 cents a share on sales of $685.9 million. A year ago the company posted earnings of $59 million, or 90 cents a share, on sales of $638.6 million. Looking ahead, Beckman forecast first-quarter earnings of 59 cents to 66 cents a share on sales growth of 6% to 9%. Analysts are expecting earnings of 64 cents a share on sales of $573.6 million, or sales growth of about 6.9%. Shares traded down $4.78 to $66.40.

Shares of

Idexx Laboratories

(IDXX) - Get Report

fell 2% Friday after the maker of diagnostic products posted solid fourth-quarter results but warned that first-quarter earnings would fall below expectations. The company earned $16.9 million, or 49 cents a share, on sales of $144.3 million. Analysts were expecting earnings of 48 cents a share on sales of $134.5 million. Looking ahead, Idexx forecast first-quarter earnings of 50 cents to 51 cents a share on sales of $152 million to $154 million. The forecast excludes an acquisition-related charge of 3 cents a share. Analysts had been expecting earnings of 53 cents a share on sales of about $145 million. Shares traded down $1.15 to $55.93.

Vasogen

( VSGN) fell 1.6% after the company said it plans to sell 9 million shares of stock for $4.70 a share, resulting in net proceeds of about $39.3 million. The stock is being sold as part of an existing shelf registration filed with the

Securities and Exchange Commission

. The stock sale represents a 9% discount to Vasogen's closing price of $5.14 on Thursday. The company intends to use the proceeds to fund ongoing development of its Celacade technology, to fund its drug development pipeline, and for general corporate purposes. Shares traded down 8 cents to $5.06.

Shares of

McKesson

(MCK) - Get Report

rose 10.6% after the drug distributor posted third-quarter earnings above expectations. Excluding a securities litigation charge, the company earned $145 million, or 49 cents a share, on sales of $20.8 billion. Analysts were expecting earnings of 45 cents a share. A year ago the company earned $120 million, or 41 cents a share, on sales of $18.2 million.

The company's pharmaceutical sales jumped 14% in the latest quarter to $19.7 billion. Excluding warehouse sales, pharmaceutical sales rose 19%. Warehouse sales, meanwhile, rose 6% during the quarter, despite one less selling day compared with a year ago. The company's medical-surgical sales grew 3% to $736 million, though operating income fell 5% to $24.7 million. Looking ahead, McKesson narrowed its 2005 earnings guidance to $2.05 to $2.15 a share. Previously, it expected $2 to $2.20 a share. Analysts are expecting earnings of $1.94 a share. Shares of McKesson traded up $3.20 to $33.54.

Other health care movers included

Merck

(MRK) - Get Report

, down $3.16 to $28.02;

Pfizer

(PFE) - Get Report

, down 33 cents to $24.35;

Aastrom Biosciences

(ASTM)

, up 17 cents to $3.19;

Teva Pharmaceutical

(TEVA) - Get Report

, up 60 cents to $28.31;

Schering-Plough

( SGP), down 13 cents to $18.87;

Johnson & Johnson

(JNJ) - Get Report

, up 40 cents to $64.62;

StemCells

(STEM)

, up 38 cents to $4.88; and

Geron

(GERN) - Get Report

, down 5 cents to $8.08.