Recently developed drugs called TNF-blockers have brought relief to many people with inflammatory conditions such as rheumatoid arthritis or the intestinal disorder, Crohn’s disease. However, the drugs do carry a risk.

In a report released on Thursday, federal health officials at the Centers for Disease Control and Prevention in Atlanta point out that patients taking TNF-alpha antagonists, such as Remicade (infliximab), Enbrel (etanercept), and Humira (adalimumab) have an increased risk of tuberculosis.

As of January 2004, “several hundred reports” of active TB disease in patients taking drugs in this class had been received by the U.S. Food and Drug Administration’s adverse-event reporting system, according to an article in the Morbidity and Mortality Weekly Report.

While most of these cases occurred outside the U.S., where the risk of TB infection is higher, the report describes 12 instances of active tuberculosis diagnosed among Californians who were being treated with TNF-blockers.

Eleven patients had TB disease after taking Remicade and one while on Enbrel therapy. Most of the cases probably represent progression of latent TB infection to active TB disease, according to CDC, because all but one patient had at least one risk factor for having latent TB.

In some of these cases, patients had not been screened for TB prior to starting TNF-blocker therapy.

Testing for TB involves measuring the reaction to a tuberculin skin test, but the CDC notes that many patients who need TNF-blockers may also be less sensitive to tuberculin because of their underlying condition or its treatment. Therefore, “tuberculin skin test results at the time of initiating TNF-alpha antagonist therapy might be falsely negative.”

The CDC recommends that doctors consider treating latent TB in patients with negative tuberculin test results whose circumstances “suggest a probability” of latent TB.

Postponing TNF-blocker therapy, when possible, until treatment of TB is complete, should also be considered.

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SOURCE: Morbidity and Mortality Weekly Report, August 6, 2004.