Progressive multifocal
leukoencephalopathy (PML)

June 2007     View PDF     En español

Cytosine arabinoside (Ara-C)

Cytosine arabinoside (ara-C, cytarabine, Cytosar-Ur) is currently used as chemotherapy for leukemia and cancer. For treating PML it was commonly given through a shunt into the brain and/or directly into a vein (intravenously). Experienced neurologists may dose ara-C through a shunt (called intrathecally) into the brain at doses of 10mg/m2 for three days, followed by 10mg/m2 twice a week for two weeks, then 20–30mg/m2 each week thereafter. The common dose of ara-C when given into a vein is 2mg/kg in 5-day cycles, every 15 or 30 days.

Side effects include nausea, consistent fevers and bone marrow toxicity. These effects are dependent on its dose and schedule and vary in severity. Ara-C can harm an unborn child in pregnant women. Checking blood work is necessary, including daily platelet, leukocyte counts and bone marrow exams during treatment. Some doctors give a dose of G-CSF (granulocyte colony stimulating factor, Neupogen) for one week before starting ara-C to relieve bone marrow toxicity. Prednisone may help reduce side affects.

While ara-C was once considered standard-of-care for people with PML who chose treatment, it has fallen out of favor due to its side effects, low success rate and the superior responses seen from using potent anti-HIV therapy.
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