By Gene Emery BOSTON, Jan 10 (Reuters) - Pregnant women who are HIV-positive and take the drug nevirapine during labor to prevent infecting their babies should wait until six months after delivery to resume taking the drug to avoid developing resistance, a new study showed. By following the findings, to be published in The New England Journal of Medicine on Thursday, mothers could reduce the chance of the AIDS drug failing to work when they need it for themselves. It translates into very clear policy for how to treat AIDS in new mothers who received nevirapine to protect their infants, said Max Essex, an author of the study, which followed the cases of 218 women in Botswana. The study will be most important in poor countries where nevirapine-based therapy may be the only treatment available to shield a baby from the AIDS virus during delivery. Once the drug is used, the risk of an already infected mother developing resistance to it is high. Up to 69 percent of the women who receive a single dose of the drug discover that the AIDS virus quickly develops a resistance to it. In cases where the drug fails to protect the baby, the infant can develop a resistance as well. But if the virus doesn't see nevirapine for six months after the initial dose, the drug retains its effectiveness, said Essex of the Harvard School of Public Health. Nearly 42 percent of the women who started receiving nevirapine within six months of their baby's delivery developed a resistance to the drug, compared to 12 percent who did not receive it until at least six months after delivery. The drug is often given as a combination, known as ART. "If you can wait six months to administer nevirapine-based ART, do so," said Essex. "If not, treat only with combinations of drugs that do not contain nevirapine or nevirapine-related drugs. Implementing this policy can improve the health of women who need AIDS treatment." Nevirapine is sold under the brand name Viramune by the privately held Boehringer Ingelheim.
