Single-dose Viread (tenofovir) plus Emtriva (emtricitabine) can greatly reduce the risk of HIV resistance to non-nucleoside reverse transcriptase inhibitors (NNRTIs) in HIV-positive pregnant women using one-time administration of the NNRTI Viramune (nevirapine) at the time of delivery. This finding, to be reported in an upcoming edition of The Lancet, has significant implications in developing nations where single-dose Viramune is frequently used to reduce the risk of perinatal HIV transmission from mother to child at the time of birth, but may also increase the risk of developing lasting resistance to the drug and other NNRTIs.
Previous studies have demonstrated that single-dose Viramune can reduce the risk of mother-to-child HIV transmission by 40 percent when it is given at the onset of labor, making it a safe, cheap, and easy-to-use prevention strategy, particularly in countries with limited health care resources. Unfortunately, single-dose Viramune causes high-level HIV drug resistance to NNRTIs in up to 75 percent of HIV-positive women and 87 percent of infants who do become infected with HIV.
By adding single-dose Viread and Emtriva—coformulated as Truvada in some countries—to the Viramune, the risk of resistance to Viramune and cross-resistance to other NNRTIs drops by 53 percent, according to the study conducted by Benjamin Chi, MD, of the Centre for Infectious Disease Research in Zambia, and his colleagues. The study, involving 398 HIV-positive pregnant women who received a short course of Retrovir (zidovudine) plus Viramune at the time of delivery either with or without Viread and Emtriva, looked for evidence of Viramune and NNRTI resistance at weeks 2 and 6 after receiving the Viramune dose.
While Dr. Chi’s group commented that single-dose preventive therapy involving a combination of drugs still suffers from limited efficacy—the risk of mother-to-child HIV transmission has been reduced by approximately 90 percent in countries using combination HIV drug treatment and state-of-the-art prenatal care—the addition of single-dose Viread and Emtriva “is an important adjunct to regimens that incorporate intrapartum nevirapine and should be considered in settings where drug combinations to be taken over several days might be impractical for patients or for local health infrastructure.”
