Updated from 2:26 p.m. EST with new stock prices

Earnings, regulatory and government actions and generic-drug strategy all factored into a fairly positive day for health stocks Friday.

Medical device maker Intuitive Surgical ( ISRG) said Thursday post-close that fourth-quarter net income more than doubled to $49.2 million, or $1.24 a share, from $23.6 million, or 62 cents a share, a year ago. Revenue increased 68% to $189.4 million from $112.6 million in the year-ago quarter, driven by higher use and sales of the da Vinci Surgical System. Analysts polled by Thomson Financial had estimated profit would be $1.04 a share on revenue of $175.9 million. Shares were up a whopping $51.61 on Friday, or 20.3%, to $305.61.

Also on the uptick, Affymetrix ( AFFX) said Thursday post-close that net income climbed to $12.8 million, or 17 cents a share, from $8.7 million, or 13 cents a share, in the comparable year-ago quarter. The company reported earning 20 cents a share when restructuring charges are factored out, on revenue of $107.6 million.

Analysts surveyed by Thomson Financial expected profit of 16 cents a share on revenue of $108.9 million. Looking ahead, the company expects total revenue in the range of $505 million to $525 million.

Shares were up $1.97, or 9.8%, to $22.03. The stock is a component of the Nasdaq biotechnology index, which was up 16.54, or 2.1%, to 821.64.

However, not everyone was up -- Mentor ( MNT) said Thursday post-close that net income for its three months ended Dec. 31 fell to $11.9 million, or 32 cents a share, compared with $13.6 million, or 29 cents a share, in the year-ago quarter when the company had more shares outstanding. Excluding items, Mentor earned 37 cents a share vs. 32 cents in the year-earlier period. Analysts surveyed by Thomson Financial forecast earnings of 31 cents a share, on revenue of $93 million. Shares were down $1.70, or 4.9%, to $32.68.

Also, away from earnings, Biovail ( BVF) said Friday that it faces a government probe regarding its blood-pressure drug Cardizem LA, which could lead to civil and criminal charges. In July 2003, the company received a subpoena from the U.S. Attorney's Office for the District of Massachusetts regarding the promotional and marketing activities for Cardizem's commercial launch, and then Friday the company said the U.S. Attorney's Office in Boston notified it that it is the focus of a federal grand-jury investigation. Shares were down 46 cents, or 3.4%, at $13.24.

Meanwhile, with better news, Medtronic ( MDT) received approval from the U.S. Food and Drug Administration (FDA) for the Endeavor drug-eluting coronary stent system to treat coronary artery disease. The stents are wire mesh tubes used to prop open arteries that have cleared of blockages, restoring blood flow to the heart -- the drug-eluting variety are coated with medicine to reduce the risk that the artery will narrow again and require a repeat surgery.

The company said the disease, which is the leading cause of death in the U.S., affects an estimated 13 million people in the country. Shares were trading up $1.35, or 2.9%, to $47.85.

And finally, Teva Pharmaceutical Industries ( TEVA) said it has not relaunched and does not intend to ship additional units of generic acid-reflux treatment Protonix at this time.

Earlier this week, the Israeli generic-drug maker and Wyeth ended their standstill agreement for patent litigation on generic Protonix. Wyeth, and partner Nycomed, said it would begin marketing its own generic version of the drug, which was due to see patent expiration in 2010. The move gave Teva the freedom to resume sales of generic Protonix, which it originally introduced in December, however it said today that it is not doing so at this time.

Wyeth ( WYE) said earlier in the week that it continues to seek an injunction against any infringement of the patent, as well as monetary damages, including lost profits, from Teva. Teva was trading down 46 cents, or 1%, at $45.58 on lighter-than-average volume. Wyeth was up 3.5% at $41.05.