Antiretroviral drugs

Antiretroviral drugs

Treatment for the mother

Women who have reached the advanced stages of HIV disease require a combination of antiretroviral drugs for their own health. This treatment, which must be taken every day for the rest of a woman's life, is also highly effective at preventing mother-to-child transmission (PMTCT). Women who require treatment will usually be advised to take it, beginning either immediately or after the first trimester. Their newborn babies will usually be given a course of treatment for the first few days or weeks of life, to lower the risk even further.

Pregnant women who do not yet need treatment for their own HIV infection can take a short course of drugs to help protect their unborn babies. The main options are outlined below, in order of complexity and effectiveness.

Single dose nevirapine

The simplest of all PMTCT drug regimens was tested in the HIVNET 012 trial, which took place in Uganda between 1997 and 1999. This study found that a single dose of nevirapine given to the mother at the onset of labour and to the baby after delivery roughly halved the rate of HIV transmission.^{5 6} As it is given only once to the mother and baby, single dose nevirapine is relatively cheap and easy to administer. Since 2000, many thousands of babies in resource-poor countries have benefited from this simple intervention, which has been the mainstay of many PMTCT programmes.

When is single dose nevirapine appropriate?

A significant concern about the use of single dose nevirapine is drug resistance. Around a third of women who take single dose nevirapine develop drug resistant HIV,⁷ which can make subsequent treatment involving nevirapine and efavirenz (a related drug) less effective.⁸ Studies have found that drug resistance resulting from single dose nevirapine tends to decrease over time; if a mother waits at least six months before beginning treatment then it may be less likely to fail.^{9 10} Nevertheless, in some cases the drug resistant HIV persists for many months in some parts of the body, even if it cannot be detected in the blood, and this may undermine the longer term effectiveness of treatment.¹¹

Whenever possible, women should receive a combination of drugs to prevent HIV resistance problems and to decrease MTCT rates even further.

Among babies infected with HIV and exposed to single-dose nevirapine, around half have drug resistance at 6-8 weeks old.¹² Other infants may become infected with drug resistant HIV through breastfeeding.¹³

Because of concerns about drug resistance and relatively low effectiveness, there is now general agreement that single dose nevirapine should be used only when no alternative PMTCT drug regimen is available. Whenever possible, women should receive a combination of drugs to prevent HIV resistance problems and to decrease MTCT rates even further.

Nevirapine, however, is still the only single dose drug available to prevent MTCT. Other "short course" treatments require women to take drugs during and after pregnancy as well as during labour and delivery. This means they are much more expensive and more difficult to implement in resource poor settings than nevirapine, which can be used with little or no medical supervision at all. So, for now, single dose nevirapine remains the only practical choice for PMTCT of HIV in areas with minimal medical resources.

Combining AZT with single dose nevirapine

According to the World Health Organization (WHO) 2006 guidelines, the recommended course of drugs for preventing mother to child transmission (PMTCT) in resources-limited settings should be a combination of AZT and single dose NVP. This approach is much more difficult to administer than single dose nevirapine on its own, but it is also significantly more effective, and is less likely to lead to drug resistance. AZT was first shown to reduce MTCT rates in 1994, and is the best-studied drug for this purpose.