A new, inexpensive nevirapine regimen for reducing mother to child transmission of HIV has been reported, and holds promise for use in developing countries. The regimen was used in a study carried out in Uganda and was found to be more effective than a zidovudine regimen (Lancet 1999;354:795).
The study was designed to provide the neonate with antiretroviral prophylaxis during labour, delivery and in the first week of life.
A group of 626 HIV-infected pregnant women were randomly assigned to receive either nevirapine or zidovudine. The nevirapine regimen consisted of a single oral 200mg dose given to the mother at the onset of labour and a 2mg/kg dose of nevirapine oral suspension given to the newborn within 72 hours of birth. In the other group, a dose of 600mg of zidovudine was given at the onset of labour and 300mg every three hours until delivery; a dose of 4mg/kg zidovudine was given twice daily to the newborn for the first seven days after delivery.
Nearly all babies were breastfed. Results are available so far on HIV status of the babies aged 14-16 weeks. At this point, HIV transmission rates were 25.1 per cent in the zidovudine group and 13.1 per cent in the nevirapine group. The researchers conclude that "nevirapine lowered the risk of HIV-1 transmission during the first 14-16 weeks of life by nearly 50 per cent."
Discussing possible reasons for the differing efficacy of the two drugs, the researchers note that, unlike zidovudine, nevirapine is active immediately against intracellular and extracellular virus, and does not have to be taken up by the cell and metabolised to its active form. The drug could therefore be more effective than zidovudine when given close to the time of exposure and may have had a more striking effect in decreasing viral load in colostrum and early breast milk samples. The researchers add that nevirapine has a long half life compared with zidovudine and that variability of drug concentrations during the first week of life is expected to be much less than with zidovudine, which requires multiple dosing to maintain virucidal concentrations. "Maintenance of an effective prophylactic drug concentration during the first week of life, when additional HIV exposure may occur through breast milk, may be important in explaining the relative efficacy of nevirapine compared with zidovudine in a breastfeeding population," the researchers say.
A number of effective multidose zidovudine regimens for preventing mother to baby HIV transmission have been identified but none is in widespread use in less developed countries.
The authors of the new study say that their regimen is simple and inexpensive but that there are obstructions to implementation. One problem is that routine HIV testing of pregnant women is often not available. Until counselling and testing infrastructures are in place, one option might be to provide all pregnant women in high HIV seroprevalence areas with nevirapine before or at onset of labour, if the drug proves to be safe in long-term follow up, they say.