Health stocks ended the week without fireworks but with continued Vytorin discussions, earnings and regulatory actions -- and interactions.

Merck ( MRK) and Schering-Plough ( SGP) issued a response on Friday to the criticism of the companies' handling of Vytorin, the Zetia-plus-statin drug that in a clinical trial (called Enhance) showed no advantage to lessening plaque buildup in arteries over a statin alone. The pricier Vytorin, which has been shown to lower cholesterol more so than statins, has been the center of questions as speculation swirls about the reasoning behind the long-delayed release of the Enhance trial data and the implications of the results.

The companies said they strongly object to mischaracterizations about the study. "While the ENHANCE trial was time consuming and took longer than originally anticipated to complete, our companies acted with integrity and good faith in connection with the trial. We took numerous actions to assure the quality of the reading of the ultrasound images," said Thomas Koestler, president of Schering-Plough Research Institute in a release.

The Food and Drug Administration then held a press briefing Friday afternoon, noting that the lowering of LDL cholesterol is a widely accepted measure of the success of lipid-lowering drugs and an accepted endpoint that's the basis for approval for such drugs. The agency said that it doesn't require the reduction cardiovascular risk or stroke in order to approve such drugs, and noted that it wouldn't change its approval process for such drugs at this point.

The FDA said it could be late this year before it will be able to complete a review of the study results. And it will remain to be seen until data from another study is available in 2011 whether the reduction in cholesterol translates into reduced risk of adverse cardiovascular events. Watch for more coverage on the FDA briefing and the Merck/Schering data from TheStreet.com writer Melissa Davis.

Merck traded down 3.6% to $47.79, and Schering-Plough fell 5.7% to $19.02. Both stocks are components of the Amex pharmaceutical index, which was down 2.2% at 314.21.

Cephalon ( CEPH) said Friday that the FDA accepted the company's supplemental new-drug application (sNDA) for Fentora for the management of breakthrough pain in opioid-tolerant patients with chronic pain. But the agency notified the Company that it will convene an advisory committee panel on May 6 to consider the application. The FDA often calls a panel of experts to discuss questions or concerns about data or a product in general, and typically takes the panels' recommendation on whether to approve it, although it's not bound to. Shares fell 4.7% to $65.86.

Amgen ( AMGN) shares were up on Friday, after Thursday postclose the company divulged quarterly and year-end earnings , and separately released positive data on osteoperosis drug Denosumab.

The company said adjusted earnings for the recent quarter came in at roughly $1.09 billion, or $1 a share, on an adjusted basis (a 11% increase from the year-ago quarter) on revenue of $3.7 billion, a 2% decrease year over year. The company edged past expectations of Wall Street analysts who were looking on average for 97 cents a share on revenue of $3.56 billion.

For the year, Amgen reported adjusted earnings of $4.8 billion, or $4.29 a share, on revenue of $14.8 billion, also high in comparison to the Street consensus of $4.26 a share on revenue of $14.57 billion. Quarterly worldwide sales of anemia drug Aranesp fell 25% year over year to $827 million, and sales of Epogen fell 3% year over year.

Looking ahead, Amgen expects 2008 adjusted earnings in the range of $4 to $4.30, on revenue ranging from $14.2 billion to $14.6 billion. Analysts were expecting $4.37 a share on revenue of $14.48 million. Shares were up 4.4% at $48.14 on Friday.

Also, device maker Cardica ( CRDC) said Thursday after the close that second-quarter revenue came in at $1.7 million, vs. $900,000 in the year-ago quarter. It reported a net loss of $4.2 million, or 29 cents a share, compared with a net loss of approximately $2.5 million, or 23 cents a share, for the fiscal 2007 second quarter.

For fiscal 2008, the company predicts total revenue of $6 million to $8 million and a net loss of between $16 million and $18 million. Shares were down 11.6% at $8.08.