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Drug Resistancet Fades Quickly in Key Aids2 Drug One of the main weapons to prevent mother-to-child transmission of the AIDS virus during birth is the drug nevirapine3. But when nevirapine is used alone just once, HIV4 starts becoming resistant to it. Research in Botswana shows that the resistance is not long lasting and that this affordable drug does not have to be abandoned forever by infected mothers who have already taken it. International medical guidelines call for5 pregnant women with advanced HIV to get a combination of AIDS drugs including nevirapine to prevent passing their infection on to their newborns during delivery. But in poor countries, combinations have been expensive and nevirapine has often been Used al. one, since studies have shown that a single dose can cut the transmission rate in half. The problem is that HIV resistance builds against it quickly when used alone just once because other drugs are not present to kill the virus particles that survive nevirapine. This renders the drug less effective in later combinations for treating women after their baby is born. But the new study from Botswana shows that nevirapine can make a comeback for these women if they wait until the resistance subsides. The further out you get from that exposure to single dose nevirapine, the less detectable nevirapine resistance is6, said Shahin Lockman of the Harvard School of Public Health in Boston7. She says waiting period for women who get the single dose of nevirapine at delivery can be as short as six months. If they started nevirapine-based treatment six or more months after nevirapine exposure, their treatment response8 was just as good, and really quite high, compared to women who did not have the single dose of nevirapine, she added. However, the women who started nevirapine-based treatment within six months of that nevirapine exposure were much more likely to experience treatment failure. | 
