NEW YORK (Associated Press) - Drugmakers Wyeth and Amgen Inc. have bolstered warnings about tuberculosis and other life-threatening infections on the label of their skin-disorder drug Enbrel.

The new boxed warning, the most serious a drug can carry, indicates patients taking the drug have contracted infections that led to hospitalization and death. The same language previously appeared in bolded text, which is considered a less serious warning.

Infections included tuberculosis, a disease which attacks the lungs, as well as bacterial sepsis, which can cause severe fever and inflammation.

The Food and Drug Administration highlighted the warnings Thursday in a posting to its Web site.

The drug manufacturers alerted doctors to the new language in a March 14 letter.

"Patients should be educated about the symptoms of infection and closely monitored for signs and symptoms of infection during and after treatment with Enbrel," states the warning label.

Enbrel is primarily used to treat psoriasis, a disorder that causes red, inflammed patches on the skin. The drug is also sometimes used to treat rheumatoid arthritis and rare autoimmune disorders.

Tuberculosis was observed in 2 Enbrel patients out of more than 20,000 studied by the companies, according to the updated labeling.

Thousand Oaks, Calif.-based Amgen and Madison, N.J.-based Wyeth co-market Enbrel in the U.S. and Canada, where it had sales of $3.2 billion in 2007.

Shares of Amgen Inc. rose $1.36, or 3.3 percent, Thursday to close at $43.23 while Wyeth shares rose $1.06, or 2.4 percent, to $45.53.