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Side Effects of MS Treatments

Other Cautions continued...

Another caution is with the drug Tysabri, which is used as a second-line treatment for people whose MS doesn't respond well to interferons or Copaxone. Tysabri is generally safe, but it can increase the risk for a rare but dangerous viral infection of the brain, called progressive multifocal leukoencephalopathy (PML). According to the FDA, PML incidence per 1,000 patients is 0.3 cases during the first two months of treatment, 1.5 cases during 25 to 36 months of treatment, and 0.9 during 37 to 48 months of treatment. 

"Even though it's relatively rare, it's a very serious disease and often fatal or disabling, so we want to make sure we minimize the risk," Miller says. The longer patients are on this drug, the greater their risk becomes. Other conditions that increase risk for PML include AIDS, cancer, organ transplant, and chronic steroid therapy or immune suppressing therapy.

A test can help doctors assess risk for PML. The test looks for evidence of exposure to the JC virus, which causes PML. In studies, all of the people taking Tysabri who developed PML had antibodies to the JC virus. "We assume that if you don't have this virus in your body, your risk of PML would be very low," Ratchford says. "The risk is still low, even among people who are JC-positive, but it is a little higher." Having this test available could make it easier for doctors and MS patients to decide whether taking the drug is worth the risk.

Aubagio is one of the new oral treatments for MS. The most common side effects of Aubagio include diarrhea, abnormal liver tests, nausea, and hair loss. However, Aubagio does carry a “black box” warning -- the FDA’s most serious warning -- because of liver problems and birth defects. Doctors should periodically do liver function testing in those on the drug. The medication should not be taken by pregnant women. 

Another oral drug is Gilenya. Before you can take this drug, you'll need to have a chickenpox vaccine if you haven't already had chickenpox. That’s because during a clinical study one person died from chickenpox while taking Gilenya. Although it isn't 100% clear that Gilenya caused the infection, "It's possible that person's ability to fight off the chickenpox virus was affected by the medication," Ratchford says. You'll also need to stay in your doctor's office to be watched for six hours the first time you get Gilenya, because it can cause a drop in heart rate after the first dose. Gilenya's most common side effects include headache, diarrhea, back pain, cough, and abnormal liver tests. The FDA says it is investigating someone in Europe who had developed PML, the brain infection mentioned above, after taking Gilenya.

Tecfidera is also an oral medication. It may cause low levels of immune cells, so your doctor will do regular blood tests to check for that. An active ingredient similar to the one in Tecfidera has been linked to four cases of PML. However, this has not been seen in patients taking Tecfidera. The four patients also had additional risk factors for PML. Tecfidera's most common side effects are flushing, stomach pain, diarrhea, nausea, and vomiting. 

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