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Tenofovir/Emtricitabine Lowers HIV Resistance in Women Given Nevirapine

LONDON, U.K. --November 6, 2007 -- Single-dose tenofovir and emtricitabine at delivery reduces HIV-viral resistance to non-nucleoside reverse transcriptase inhibitor drugs (NNRTIs) in women given intrapartum nevirapine for perinatal HIV prevention. These are the conclusions of authors of an article published early online and in an upcoming edition of The Lancet.

Nevirapine, a NNRTI, is 40% efficacious in prevention of mother-to-child HIV-1 transmission when used in labour, and is also safe, cheap, and easy-to-use -- all very important in the developing world, where half-a-million children are infected annually by the route. However, after intrapartum nevirapine, 19-75% of women and 33-87% of the minority of infants who become infected develop HIV that is resistant to NNRTIs.

Dr. Benjamin Chi, Centre for Infectious Disease Research, Zambia, and University of Birmingham, Alabama, USA, and colleagues did a randomised trial of 397 HIV-infected pregnant women who had sought care at two public sector health facilities in Lusaka. Of these, 198 were assigned a single oral dose of 300mg tenofovir disoproxil fumarate with 200mg emtricitabine under direct observation, and 199 to receive no study drug. Short-course zidovudine and intrapartum nevirapine were offered to all the women, according to the local standard of care. The primary study outcome was resistance to NNRTIs at six weeks post-delivery.

The researchers found that women given the intervention were 53% less likely than controls to have a mutation that conferred resistance to NNRTIs six weeks after delivery. The absolute risk of this was 12% for the intervention group and 25% for the control group. Whilst there were serious adverse events for mothers (postpartum anaemia) and children (septicaemia, pneumonia) in both intervention and control groups, none were judged to be caused by the intervention.

They conclude: "We showed that a single dose of tenofovir and emtricitabine -- taken with antepartum zidovudine and intrapartum nevirapine -- can substantially reduce non-nucleoside reverse transcriptase inhibitor resistance mutations at two weeks and six weeks after ingestion. Despite its effectiveness, this intervention might need modification to provide the optimum protective effect. Nevertheless, it 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."

In an accompanying Comment, Dr. Shahin Lockman and Dr. James McIntrye, Brigham and Women's Hospital, Harvard School of Public Health, Boston, MA, USA, say: "Chi's results do provide strong evidence that adding single-dose tenofovir/emtricitabine to short-course ziduvudine and single-dose nevirapine in women with higher CD4+ cell counts is a new, effective, and feasible approach to reducing maternal nevirapine resistance, and one that should be seriously considered for implementation."


SOURCE: The Lancet

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