Drug resistance with Nevirapine

WHO convened an expert panel in March 2000 to review the reported NVP resistance in mother infants pairs receiving NVP as part of an MTCT-prevention package.¹⁸ The impact of these new data on the efficacy of the regimen in future pregnancies, future treatment options (of both mother and newborn), the disease progression and possibility of spread of resistant virus in the population was considered. The panel concluded that the new information was not considered sufficient to interfere with plans to make NVP more widely available in pilot MTCT-prevention programmes or in research settings. But there was insufficient information to recommend wide-scale implementation of NVP for MTCT prevention.¹⁹

At the Durban conference, the previous report from HIVNET006 of NVP-resistance observed in 20% of 15 women was confirmed in HIVNET012 where 7 of 30 transmitters showed selection of resistant virus at 6 weeks. In addition 3 of 7 infected infants showed resistance mutations.²⁰

The changing time horizon for access to ARV treatment brings a new dimension to the question of drug resistance reported in women and children exposed to Nevirapine for MTCT prevention.

Where there is a reasonable expectation that non-nucleoside reverse transcriptase inhibitors (NNRTIs) will be used as part of treatment for HIV infection in either the mother or the child, considerations about resistance suggest that the use of an MTCT-prevention regimen which does not include NVP may be preferable. However, in settings where NNRTIs are not expected to be available in the near future, the costs and operational advantages of the NVP regimen make it a very attractive option. Such issues will be discussed at a consultation to be convened by WHO in October 2000 at which all information on the efficacy and safety of different ARV regimens, and the risks of transmission through breast milk will be reviewed.