HIV Drug Resistance Risk In Mothers Reduced By Combination Of Common Drugs

Providing tenofovir and emtricitabine with nevirapine during labor greatly reduces the extent of resistance to non-nucleoside reverse transcriptate inhibitors (NNRTIs), such as nevirapine, which HIV-positive women take to lower the risk of mother-to-child transmission during childbirth.

Benjamin Chi, M.D., assistant professor of obstetrics and gynecology at UAB, and colleagues, reported their findings online in this week's edition of The Lancet. Chi said the drug combination reduced resistance to NNRTIs by more than half at six weeks after delivery. This finding is important because between 20 and 69 percent of women given nevirapine develop resistance to the NNRTIs after taking a single dose. Although resistance becomes undetectable one to two years after ingestion, there are concerns that it could still compromise a woman's future treatment options.

In this study, 399 participants were randomly assigned to receive or not receive single dose tenofovir and emtricitabine along with routine care. Routine care meant starting the anti-HIV drug zidovudine (or AZT) at 32 weeks gestation, and then ingesting a single dose of nevirapine at the start of labor. Participants were healthy and did not yet require treatment with potent antiretroviral therapy. The main goal of the study was to see if there was a difference in the presence of NNRTI resistance mutations six weeks after giving birth. The study was conducted in Lusaka, Zambia between 2005 and 2007.

Overall, 12 percent of women given the tenofovir and emtricitabine dose developed NNRTI resistance, compared to 25 percent among those who did not receive the additional drugs. Tenofovir and emtricitabine appeared to be safe, with no attributable side effects. Although these additional drugs did prevent NNRTI resistance, their use did not lead to substantial reductions in mother-to-child HIV transmission.

These results are encouraging for places like Zambia, which must rely on nevirapine for both HIV prevention and treatment. "The simplicity and effectiveness of this regimen is an important aspect of this intervention," Chi said.

"HIV-infected pregnant women who take nevirapine in labor now have an easy way to reduce some of the negative consequences associated with the drug."