More than one-fifth of HIV-positive pregnant women who take a single dose of the antiretroviral drug nevirapine to prevent mother-to-child HIV transmission have some resistance to the drug one year after treatment, according to a study published in the April 25 edition of the journal Proceedings of the National Academy of Sciences, Xinhuanet reports (Xinhuanet, 5/2). Previous studies indicated that drug resistance diminishes in women shortly after taking the drug. Sarah Palmer, manager of the Virology Core of the HIV Drug Resistance Program at the National Cancer Institute, and colleagues looked for nevirapine-resistant HIV mutations in 22 women who were given nevirapine in Soweto, South Africa (MacKenzie, New Scientist, 4/24). The researchers examined the plasma samples of the women, all of whom were living with HIV-1 subtype C. Testing using standard genotype analysis found that six of the women had nevirapine resistance two to six months after treatment, but not at one year; nine of the women had resistance at two months, but not at six months; and seven of the women had no resistance at any time, according to the study. However, researchers found that 16 of the 21 women who tested negative for nevirapine resistance one year after treatment actually had some element of resistance, which was determined using more sensitive tests. At least 23% of the women more than one year after treatment had a greater nevirapine resistance than they had before taking the drug (Palmer et al., Proceedings of the National Academy of Sciences, 4/25). "We need more effective interventions [for mother-to-child HIV transmission] that are available to everyone" Palmer said (New Scientist, 4/24).
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