Updated from 2:09 p.m.

Shares of Epix Pharmaceuticals ( EPIX) were among the worst-performing health-related stocks Friday, falling 27.2% after the Food and Drug Administration asked for more studies of a key product.

The setback came as the company received an approvable letter seeking additional clinical studies that would support the company's imaging agent, which is used to light up blood vessels that are being scanned by an MRI.

"The FDA indicated that its principal questions continue to relate to the non-contrast MRA magnetic resonance angiography comparator scans used in the Phase III trials and to the statistical treatment of the uninterpretable images," the company said. According to the company, the FDA did not raise any issues with safety or manufacturing. Epix said that it and its partner, Schering AG, would continue to work with the FDA to figure out what steps need to be taken to get MS-325 approved. Shares traded down $3.98 to $10.67.

Enpath Medical ( NPTH) fell 8.8% after the company said the FDA requested more clinical data regarding the company's Myopore steroid product. Enpath "had been proceeding on the understanding that the FDA would grant approval based upon the originally determined regulatory pathway of a paper pre-market approval -- a less burdensome approach that does not include prospective human clinical data," the company said. The FDA said it couldn't approve the PMA based on the data and labeling originally submitted. As a result, the company has provided additional animal data and analysis. The FDA has agreed, Enpath said, to review the new data to determine whether the less burdensome approach it recommended in April 2004 is still the most appropriate course of action.

If the company's product receives FDA approval in the next three months, Enpath said it would expect to reaffirm 2005 sales of $35 million to $37 million. What's more, if Myopore is launched during the second quarter, earnings for 2005 should come in between 30 cents and 40 cents a share. Shares traded down 95 cents to $9.80.

Shares of Vasomedical ( VASO) fell 10.6% after the company posted a second-quarter loss of 3 cents a share on a 29% drop in sales. In the year-ago period, the company posted a loss of $2.09 million, or 4 cents a share. "The decline in revenue reflects lower sales and average selling prices of our EECP systems, which were partially offset by higher revenues in service and rentals," the company said. Shares were trading down 11 cents to 93 cents.

Other health care movers included Pfizer ( PFE), down 8 cents to $25.25; Aastrom Biosciences ( ASTM), up 12 cents to $2.70; Schering-Plough ( SGP), down 35 cents to $20.30; Amgen ( AMGN), down 8 cents to $63.81; and Merck ( MRK), up 22 cents to $30.87.