South Africa’s Medicines Control Council this week recommended that nevirapine should no longer be used as the sole drug in short course antiretroviral treatment to prevent mother to child transmission.
Their decision follows new guidelines from the World Health Organisation recommending that, wherever possible, a combination of drugs is preferable in order to avoid the risk that nevirapine monotherapy will give rise to nevirapine resistance that might compromise the mother’s future response to treatment.
WHO made its decision in February just before the public unveiling of results from a Thai study which showed that mothers exposed to short course nevirapine had a significantly poorer response to a triple ARV regimen containing nevirapine if they started combination therapy less than six months after childbirth.
Nevirapine gives rise to resistance when used alone because the drug has a very long half life and because only one mutation needs to emerge for high level resistance to the drug.
Further findings from the Thai study were presented this week at the Fifteenth International AIDS Conference in Bangkok. They showed that 41% of women exposed to nevirapine had evidence of resistance to the drug a median of 12 days after delivery, and multiple resistance mutations were associated with higher viral load (p<0.001).
A South African study due to be presented on Thursday at the Fifteenth International AIDS Conference will show that seven days of AZT/3TC treatment after delivery for mothers and infants who received a single dose of nevirapine at delivery resulted in a substantial reduction in the risk of transmission compared to short course nevirapine alone.