AIDS drug to protect fetus is safe for infected mothers, study finds

The results are good news for poor women in Africa, Asia and Latin America who must take nevirapine, an inexpensive first-line drug that often prevents the transmission of H.I.V. from mother to child.

The drug lingers in the blood up to three weeks, and if the mother has the virus that causes AIDS, its presence encourages the growth of nevirapine-resistant strains. That has led to fears that any antiretroviral drug cocktail containing nevirapine would be useless.

But the new study, published in The New England Journal of Medicine, finds that such a cocktail is still effective if women simply delay it for six months after taking the protective dose of nevirapine.

The study was done by Harvard researchers working in Botswana but has implications for poor women everywhere. Early reports of data gathered in the study, along with evidence from similar ones, influenced the World Health Organization's new AIDS treatment guidelines last year, helping to keep nevirapine in the arsenal of first-line AIDS drugs.

Nevirapine has never been a perfect drug in prolonged use, it can poison the liver and cause rashes, and the virus that causes AIDS only needs to make a single mutation to develop resistance to it.

The drug is so simple and effective that health workers in small clinics often leave pregnant women one pill to take when labor starts and a syringe full of liquid nevirapine to squirt into the newborn's mouth, said Dr. Shahin Lockman, a researcher for the Harvard School of Public Health's AIDS Initiative and one of the authors of the study. In some cases, she said, they must do this without even knowing whether the mother is infected. In Africa, many women still refuse AIDS tests for fear family or neighbors will shun them if they prove positive.

Under those circumstances, nevirapine is usually harmless and cuts in half the chance that the baby will get infected.

The drug is also a cornerstone of antiretroviral AIDS treatment in poor countries. It is commonly found in the three-in-one pills used in treatment programs supported by Western donors, and many start-up programs have few alternatives or none at all. In generic form, it costs one-eighth as much as efavirenz, the most closely related drug.

The Botswana study concludes that waiting six months after single-dose nevirapine allows the nevirapine-resistant strains to disappear from the body.