One of the main weapons to prevent
mother-to-child transmission of the AIDS virus during birth is the drug
nevirapine. But when nevirapine is used alone just once, HIV 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. VOA's
David McAlary reports.
International medical guidelines
call for 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 alone, since studies have shown that a single dose can cut the transmission rate in
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 is," said Shahin
Lockman of the Harvard School of Public Health in Boston.
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 response 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."
The study published in the New England Journal of Medicine shows that
waiting at least six months means that HIV-positive women are 70 percent
more likely to benefit from nevirapine-based drug combinations again than
women who get them sooner.
An official with the U.S. government health agency that helped fund the
study calls it very important.
Lynne Mofenson is chief of research on child, adolescent, and maternal
AIDS at the U.S. National Institute of Child Health and Human Development.
She says the finding supports a World Health Organization (WHO)
recommendation restricting a single dose of nevirapine only to pregnant
HIV-infected women who are healthy enough to wait six months after
childbirth for more nevirapine-based therapy. Otherwise, they should get
other drugs during labor.
"It shows the importance of screening women for treatment while they
are pregnant and putting them on appropriate therapy while they are
pregnant to avoid having to start them too soon after they received
preventive therapy," she explained.
Shahin Lockman in Boston says the problem of nevirapine resistance
should diminish now that more and more people are receiving combinations
of AIDS drugs under expanded U.S. and international programs to deliver
them to Africa and other regions hard hit by the virus.