HIV drug can persist in mothers' milk: study

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(Xinhua)
Updated: 2008-08-06 13:47

WASHINGTON -- A drug commonly used in the developing world to prevent transmission of HIV from mother to child persists in the breast milk and blood of the mothers, putting them and their babies at risk of developing drug-resistant strains of the virus, a Stanford University research team reported Tuesday.

The researchers found that the drug, nevirapine, stays in the blood and breast milk of the infected mothers for at least two weeks. During that time, the virus has ample opportunity to transform itself into drug-resistant strains of HIV, the human immunodeficiency virus that causes AIDS, making it very difficult to treat.

"In the short term, nevirapine is better than nothing," said David Katzenstein, the study's lead author. "But in the long term, I'm concerned about conferring resistance. If you're talking about resistance on a broad scale, it could jeopardize future treatment for mothers and infants."

The centerpiece of public health programs in the developing world to stop mother-to-child transmission of HIV are both zidovudine (AZT) and nevirapine, which have been used as preventive tools in nearly 900,000 women and infants worldwide.

The drugs are relatively inexpensive and easy to administer, and nevirapine is typically given as a single pill as the mother goes into labor and as a liquid to the baby just after birth. Use of the drug reduces the chance of HIV transmission by half, to about 13 percent.

In addition, nevirapine has proven to be problematic. Previous studies have found that as many as 69 percent of HIV-positive mothers and as many as 80 percent of babies born infected, even after being given a single dose of nevirapine without AZT, may develop nevirapine-resistant strains of the virus.

In the latest study, the Stanford scientists finally figured out what's behind this problem.

The longer the drug remains in the system, the more likely it is to promote development of mutations in the virus. Although none of the HIV-infected women carried drug-resistant strains of the virus at the outset of the study, two months after birth RNA tests showed a third of them had drug-resistant virus in their blood. Sixty-five percent had drug-resistant strains in their breast milk as well, with the potential to pass this on to their babies through breastfeeding, a common mode of viral transmission, according to the study.

If these women had access to better, combination antiretroviral treatment to optimally suppress virus replication, they might be less likely to develop these hard-to-treat strains later, said the researchers.