Highlights
Natalizumab (Tysabri)
- In June 2006, the FDA allowed natalizumab (Tysabri) to return to the market, but with certain restrictions. Natalizumab is only for patients who have not responded to other multiple sclerosis drugs. Patients who receive natalizumab must enroll in a special program run by the drug’s manufacturer. Natalizumab was withdrawn in 2005 after reports that it caused progressive multifocal leukoencephalopathy (PML), a serious neurological disease.
- The benefits of natalizumab may outweigh the risks, according to several studies published in 2006 in the New England Journal of Medicine. The studies showed that natalizumab helps prevent relapse and disability. In one study, natalizumab slowed the rate of relapses by 68% when the drug was used as a single therapy.
- Another study suggested a very low risk of PML when natalizumab is used for a relatively short period of time. The study found that patients who received natalizumab for an average of 18 months had around a 1 in 1,000 risk of developing PML. The risks for longer-term treatment are unknown.
Interferon Drug Warning
Interferon beta 1-a (Avonex) and interferon beta 1-b (Betaseron) may cause serious liver damage and possible liver failure. Patients who take interferon drugs should have regular liver function tests, especially when they begin drug treatment. They should also avoid drinking alcoholic beverages while taking interferon.
Risk Factors
- Epstein Barr virus (EBV), which causes mononucleosis, may be associated with multiple sclerosis. Some people who develop multiple sclerosis many years after EBV infection have abnormally high levels of antibodies to the virus in their blood.
- Birth control pills may reduce a women’s risk of developing multiple sclerosis, suggests a study in the Archives of Neurology. Researchers think that estrogen has a protective effect.
