A newly published study says the painkiller Celebrex from Pfizer (NYSE:PFE) doubles a patient's risk of heart attack. The study does not address the increased likelihood of lawsuits being filed against the pharmaceutical, but reports have been heard of an outbreak of smiling trial lawyers.

Celebrex is one of the now-notorious class of drugs known as COX-2 inhibitors that shares space with Merck's (NYSE:MRK) Vioxx and another Pfizer drug called Bextra. Celebrex is unique, however, in that it's the only painkiller of that type still on the market. Vioxx and Bextra were voluntarily withdrawn in 2004 and 2005, when concerns over their safety were raised.

COX-2 inhibitors belong to a class of painkillers called non-steroidal anti-inflammatory drugs, or NSAIDs, which also include apparently less lethal compounds such as aspirin, ibuprofen, and naproxen. COX-2 inhibitors selectively block an enzyme that impedes the production of the pain and swelling messengers in the body that are commonly associated with arthritis.

At their height, COX-2 inhibitors were popularly prescribed drugs. In 2003, its last full year on the market, Vioxx generated $2.5 billion in sales for Merck, while Bextra earned $1.3 billion in 2004. Meanwhile, although Celebrex is projected to earn more than $2.2 billion for Pfizer this year, up from $1.7 billion in 2005, that figure is still down appreciably from the $3.3 billion it had earned the year before.

Merck now faces nearly 10,000 lawsuits over Vioxx. Four trials have already been held and Merck has emerged victorious in three of them, but that was primarily because the patients did not fall into the high-risk category where the potential for heart attacks increased significantly. Merck, a selection of Motley Fool Income Investor, has admitted that taking Vioxx for more than 18 months doubles the likelihood of heart failure, but many of those jumping on the lawsuit bandwagon had taken the drug for considerably less time than that -- sometimes weeks or even days. Though Merck will probably prevail in many of these cases because of situations like that, it still faces a staggering financial liability. In the one case Merck lost, a Texas jury awarded the plaintiff $253 million, but because of that state's laws, the pharmaceutical's damage will be capped at about one-tenth of that amount.

All of this news does not bode well for Pfizer. Though it was allowed to continue to market Celebrex with a so-called "black box warning" that tells users of the potential for heart attacks, strokes, and gastrointestinal bleeding (it's the most severe label the Food and Drug Administration imposes), the new study could spur a new round of lawsuits, since it says the risk of heart attacks caused by Celebrex is "similar in magnitude" to the risk caused by Vioxx. Pfizer, a Motley Fool Inside Value recommendation, already faces some 450 suits over Celebrex, and the first one is scheduled to go to trial in June.

Though it probably wouldn't help Pfizer at this point, the FDA has proposed preventing alleged victims from suing pharmaceuticals in state court if the agency has approved a drug as safe. Of the 9,200 lawsuits filed against Merck, almost half are at the state level, where juries can be more sympathetic to the patient. It also allows the trial lawyers to shop around for the best courts in which to sue.

Needless to say, limiting the trial lawyers' access to corporate largesse is never popular with their lobby, and it will undoubtedly prompt a sharp response.

Fool contributor Rich Duprey owns shares of Merck but of no other company mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.