BOSTON, Feb. 24 -- AIDS experts have reached the conclusion that nevirapine, the workhorse drug that has prevented tens of thousands of cases of HIV infection in newborn babies, has enough drawbacks that its use is likely to change markedly.
In the future, many HIV-infected women will probably get a mini-cocktail of AIDS drugs for weeks or months rather than the single pill now given during labor. The more complicated strategy will add work and expense to the massive effort to prevent the 2 million infected women who become pregnant each year from passing the AIDS virus to their babies.
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The current nevirapine regimen -- which requires an infant to also get a dose of the drug right after birth -- is one of the few triumphs in the global AIDS fight in the past decade. It has been used by about 500,000 women in poor countries in the past five years, by far the biggest transfer of AIDS medicines and know-how to the developing world.
The problem is that, although the astonishingly simple "single-dose" nevirapine strategies have cut the rate of HIV transmission in half, they also make many -- and possibly most -- of the women resistant to the drug.
About 350,000 people in poor countries have started taking low-priced, generic combinations of antiretroviral drugs in the past two years. The vast majority of those combinations include nevirapine. Most HIV-infected women getting pregnant now will eventually need long-term antiretroviral treatment. If their HIV becomes nevirapine-resistant before then, many treatment options will be closed off.
Beyond the issue of nevirapine-resistant HIV strains developing as a result of a single-dose strategy, the addition of one or two antiretroviral drugs to nevirapine around delivery has clear benefits: They can cut the rate of HIV transmission to babies to as low as 2 percent -- well below the 12 percent seen with the single-dose approach.
"I think we're leaving at the end of this week with a different world view," said James McIntyre, a South African AIDS researcher and expert in the mother-to-child transmission of HIV.
The issue of nevirapine's benefit and risk has been the focus of one of the more important debates in the global fight against AIDS in recent years. Data presented here, at the 12th Retrovirus Conference, have answered some of the questions.
Nevirapine's extraordinary usefulness in preventing HIV infection at birth arises from the fact that it lingers far longer in the bloodstream than any other antiretroviral drug. In many women, the medicine is still detectable in the blood 21 days after a single tablet is taken.
Although the drug's concentration during much of that period is too low to be useful, a single dose's HIV-fighting effect clearly lasts for many days. It is long enough in many cases to prevent infection both during delivery and in the first, crucial week of breast-feeding. The baby's single dose, in turn, helps protect against any virus that may get through the pharmacological blockade.