NEW YORK (Dow Jones/AP) -- Pfizer Inc. is likely to add a so-called "black box" warning to the label of its pain killer Bextra, which is similar to the recently pulled Vioxx, because it sometimes leads to a serious skin reaction.

Pfizer made the announcement in its most recent quarterly report, filed with the Securities and Exchange Commission Friday. A black-box warning is the strongest warning available for prescription drugs.

The drug has in a few cases caused Stevens Johnson syndrome, which occurs when the immune system turns on itself to rid itself of a drug, in effect burning the patient from the inside out.

It leads to severe, painful blistering of the mucous membranes and skin, according to Jean Farrell-McCawley, founder of the Stevens Johnson Syndrome Foundation. In many patients, their skin actually starts coming off in sheets, she said.

"The people are usually hospitalized in a burn unit," she said, adding that many have to be put on feeding tubes and ventilators. Stevens Johnson has about a 30 percent mortality rate, she said.

Pfizer had sent out a letter to doctors in mid-October warning them about the side effect, saying that the skin rashes have led to hospitalizations and deaths in a small number of patients. The risk is greatest during the first two weeks the drug is taken.

Bextra's label as included information about the skin reaction since 2002, Pfizer said.

Bextra is a so-called Cox-2 inhibitor, along with Pfizer's Celebrex and Merck & Co.'s Vioxx, which was pulled from the market in September because of cardiovascular side effects.

Prudential analyst Timothy Anderson wrote in a Friday research note that he expects Bextra to reach $1.7 billion in 2005 sales, contributing 15 cents a share to Pfizer's bottom line next year. But between this new warning and a "signal" of cardiovascular toxicity, this forecast may have to be revised downward, however, he wrote.

The skin reaction, known as Stevens Johnson syndrome, is included as a warning on the packages of many drugs on the market, but "few, however, have black box warnings," Anderson said.

A member of Anderson's team owns shares of Pfizer.

In the mid-October letter Pfizer sent to doctors, the company also said that there appeared to be an increased risk of stroke and heart attack when Bextra was given to very high-risk patients who had undergone coronary bypass surgery, like the one former President Bill Clinton recently had.

The company is planning long-term safety studies to test whether it affects heart attack and stroke rates in a less high-risk population.

Shares of New York-based Pfizer closed Monday at $28.41, down 38 cents, or 1.3 percent, on the New York Stock Exchange.

Elsewhere in the quarterly report, Pfizer said that it received a letter from New York Attorney General Eliot Spitzer requesting documents on clinical studies of expanded uses for drugs that are already approved. Spitzer also requested documents on the possible promotion of the drugs for unapproved uses.

Federal and state authorities have come down hard lately on drug companies for so-called off-label promotion. Drug companies are only allowed to promote their drugs for uses approved by the FDA.

The Office of the Attorney General of the State of Connecticut requested similar materials concerning Zoloft, the company's blockbuster antidepressant, Pfizer said.

On the other hand, the U.S. Attorney's Office for the District of Maryland informed the company in an Oct. 13 letter that it has closed an investigation into to the now-withdrawn diabetes drug Rezulin, which was linked to liver disease.

A federal grand jury in Maryland had sought documents from Pfizer relating to Rezulin as well as testimony from former employees of Warner-Lambert, which Pfizer acquired in 2000.

Rezulin, which was launched in 1997, was a top seller for Warner-Lambert until the company voluntarily pulled it in 2000 after two competitors' drugs hit the market -- GlaxoSmithKline PLC's Avandia and Takeda Chemical Industries Ltd.'s Actos. Both were believed to be as effective as Rezulin with fewer side effects.

URL: http://sfgate.com/cgi-bin/article.cgi?file=/news/archive/2004/11/08/financial1445EST0176.DTL