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More Doses of MS Drug Raise Risk of Brain Infection

Posted Feb 05 2010 4:31pm

By Amanda Gardner
HealthDay Reporter

FRIDAYFeb. 5 (HealthDay News) -- In the latest blow to the controversial multiple sclerosis drug Tysabrithe U.S. Food and Drug Administration on Friday announced that it was slapping a new warning on the drug's label.

In an advisory sent to health-care professionals and patientsthe FDA warned that the risk of developing progressive multifocal leukoencephalopathy (PML)a rare but deadly brain infectionincreases as more infusions are received.

"This is updated informationtaking new cases into account," explained Dr. William Sheremataprofessor emeritus of neurology at the University of Miami Miller School of Medicinewho gave the drug to the first humans.

European patients account for most of the new cases and many of them might have been taking multiple drugsraising their risk for PMLhe added.

"This is not new information. We've had this information for a couple of months now [but] the labeling in the past did not make a distinction between the time frames that people were on the drugs," said Dr. John Richertexecutive vice president for research and clinical programs at the National Multiple Sclerosis Society. "The risk-benefit ratio continues to be about the same as we anticipated since the time the drug was brought back on the market."

Another expert agreed that the clinical picture hasn't been altered by the new label warning.

"I think as long as the medication is being prescribed for the appropriate patient with MSthen the new information we have today is not going to alter medication management," said Dr. Jeffrey Tramontedirector of neurology at the Scott & White University Medical Campus in Round RockTexas. "Right nowTysabri is the most efficacious drug that's ever been approved for the treatment of relapsing-remitting MSwhich represents 85 percent of all patients out there who have MS," he said.

"Howeverit also carries the single most dangerous risk factorand that's PML," added Tramontewho only gives Tysabri if his patients have failed or have severe side effects from conventional immunomodulating drugs.

Natalizumab (Tysabri) first received FDA approval in November 2004only to be pulled from the market three months later after several patients in clinical trials developed PML.

In June 2006the FDA allowed the drug back on the marketbut with strict conditions. According to those revised guidelinesTysabri can only be administered by approved doctorsat infusion sites and at pharmacies that register and comply with a patient-safety program called CD Touchdesigned by drugmaker Biogen Idec and approved by the FDA.

The FDA said the new action was based on reports of 31 confirmed cases of PML as of Jan. 212010.

Information on the risk will also be included in the patient Medication Guide.

Howeverthe FDA did not suggest discontinuing the drugstating that it "believes that the clinical benefits of Tysabri continue to outweigh the potential risks."

The drug was approved to treat Crohn's disease in early 2008. It is also linked with liver damage. Patients do take the drug long-termRichert said.

More information

Visit the National Multiple Sclerosis Society for more on this disease.

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