What an ugly week. More health-care stocks fell by double digits over the last five days than we have seen in quite a while. Which are among the worst? Here they are -- three of the week's most horrendous health-care stocks.

On a crash diet
The crash diet continues for obesity drug pharmaceutical firm VIVUS (VVUS). The company made our horrendous list a couple of weeks ago, and now it's back. Shares plunged 24% this week.

VIVUS' stock began its most recent downward swing in mid-October after its obesity drug Qsymia was rejected by the European Medicines Agency. This week's plunge is because of a disappointing earnings report. Qsymia launched on Sept. 17, but hasn't exactly flown off the shelves, so far.

A big problem is that payers aren't covering Qsymia as much as VIVUS would like. The company reported that 30% of prescriptions aren't ultimately being filled because patients don't want to pay for the drug out of their own pockets.

Guilt by association
Orexigen Therapeutics (NASDAQ: OREX) saw its stock fall by 17% in what seems to be a case of guilt by association. Shares began declining after VIVUS reported its quarterly results. However, Orexigen reported its own results after market close on Wednesday, and shares then stabilized. 

While VIVUS must deal with the repercussions from Qsymia's slow start, Orexigen still faces a decision from the Food and Drug Administration for its obesity drug Contrave. Assuming the FDA approves Contrave, the company could be ready for its own commercial launch in late 2013.

In the meantime, Orexigen's stock performance could be linked to some degree with VIVUS and Arena Pharmaceuticals (ARNA), which makes obesity drug Belviq. Arena also appeared to be having a bad week until its stock rebounded strongly at the end of the week. Good news from the FDA, or an announcement of a partnership for marketing Contrave outside of the U.S., could serve as a positive catalyst for Orexigen and help it break from the pack.   

Not so sure
Oral fluid diagnostics company OraSure (OSUR -0.54%) doesn't look to be sure about next quarter. That uncertainty contributed to the stock falling 17% this week.

OraSure actually beat expectations for the quarter. However, the company's prediction for lower revenue and bigger losses in the fourth quarter than analysts estimated didn't go over well with investors.

Despite the weak fourth-quarter outlook, some remain bullish overall on OraSure. The company's OraQuick In-Home HIV Test just hit the market at the end of the third quarter. This new diagnostic test could be the key to better days ahead for OraSure.

Honorable mention
Several other health-care stocks trading below $2 per share had big negative swings this week. I excluded those because it doesn't take much price action to cause a double-digit move for them.

There was one big player that had a very bad week, though. Express Scripts (ESRX) shares dropped 14%. The company's earnings were pretty good. Its fourth quarter outlook was solid. But management's discussions with its customers led it to point to a not-so-rosy 2013. The stock performed horrendously this week, but kudos to executives for being transparent when they could have been less forthcoming about next year's outlook.

FYI