Drugs Used for Treating Multiple Sclerosis (cont.)

Tysabri (natalizumab)

Tysabri is used to delay the progression of physical disability and reduce the frequency of clinically important flare-ups in patients with relapsing MS. Tysabri increases the risk of progressive multifocal leukoencephalopathy, a viral infection of the brain that usually leads to death or severe disability. Therefore, Tysabri generally is reserved for patients who have had an inadequate response or are unable to tolerate other therapies for MS. The mechanism of action of Tysabri in MS is not well understood. Tysabri is a recombinant (man-made) antibody. It binds to integrins expressed on the surface of white blood cells (except neutrophils) and inhibits adhesion of the white blood cells to their receptors. Tysabri may work in MS by preventing migration of white blood cells across the blood-brain barrier from the blood and into the brain. The white blood cells may be important in promoting the inflammation of MS and the degeneration of nerves. In clinical studies Tysabri delayed the onset of sustained increase in disability. Tysabri is infused intravenously every four weeks. Side effects include headache, stomach pain, joint pain, fatigue, and depression. Progressive multifocal leukoencephalopathy, liver dysfunction, and infections also are associated with Tysabri.

What is a potassium channel blocker?

Ampyra (dalfampridine)

Ampyra is used for improving walking in patients with MS. Its mechanism of action in MS is not fully understood. Ampyra is a potassium channel blocker that prevents potassium in the blood from entering cells. It improved conduction of impulses in damaged nerves of animals by blocking potassium channels. In clinical trials Ampyra improved walking speed more than placebo. Ampyra is administered orally twice daily approximately 12 hours apart. Patients with a history of seizures, or moderate or severe renal failure should not use Ampyra. Common side effects of Ampyra include urinary tract infections, insomnia, dizziness, headache, nausea, constipation, weakness, throat pain and burning, and tingling or itchy of skin.

REFERENCES:

Prescribing Information for Avonex (interferon beta-1a); Betaseron (interferon beta-1b); Copaxone (glatiramer acetate); Rebif (interferon beta-1a); Novantrone (mitoxantrone); Tysabri (natalizumab); AMPYRA (dalfampridine)

Litzinger MH, Litzinger M. Multiple Sclerosis: A therapeutic overview. US Pharmacist 2009;34(1):HS3-HS9

Last Editorial Review: 3/3/2010 10:41:43 AM