Researchers at Johns Hopkins University, Northwestern University, and Amgen Inc. report that Filgrastim, a human growth factor sometimes taken as a supplement to anti-HIV therapy, may actually hinder the effectiveness of the HIV antiretroviral medications, AIDSWeekly reports. Filgrastim, a granulocyte colony stimulating factor, is used to reverse neutropenia in HIV-positive people and AIDS patients suffering from cytomegalovirus infections. But the researchers found that HIV viral loads dropped more slowly among those who add the compound to their anti-HIV drug regimen than those who do not take Filgrastim. The difference was slight but statistically significant, the researchers report. The compound likely interferes with the anti-HIV activity of the medications, and that allows HIV to replicate more easily.