Pills to prevent HIV raise many questions

Various trials examining the use of anti-retroviral drugs in healthy heterosexuals as a way to prevent HIV have shown drastically different results, research showed last Wednesday.

The findings of three major studies in Africa, published in the New England Journal of Medicine, raise many questions about which groups would likely benefit and how to manage such treatments in the future, doctors said.

The approach is known as pre-exposure prophylaxis, or PrEP, in which healthy people take anti-retroviral drugs – the kind used to treat people with HIV – in order to prevent getting the virus during sex with HIV-infected partners.

One study detailed in the journal which included heterosexual couples – each with one HIV-positive partner, one HIV-negative – showed a 67 to 75 per cent reduced risk of getting HIV among uninfected partners taking the drugs.

The study, known as Partners PrEP, ran from 2008 to 2010 in Kenya and Uganda and included more than 4,700 couples. It randomly assigned the HIV-negative partners to once-daily tenofovir, a combination of tenofovir-emtricitabine, or a placebo.

Both treatments showed “significant” and a “similar magnitude” of protection for both men and women, the study said.

Adherence to the drug regimen was also high in this study, with 82 per cent of samples from randomly selected participants showing detectable drug levels, and study authors estimating an overall 92 per cent adherence rate.

Another study detailed in the journal however was stopped early in April 2011 because the group receiving the drug did not show any better level of protection than the group taking the sugar pill.

That study, known as FEM-PrEP, was a randomised trial of 2,120 women in Kenya, South Africa and Tanzania.

Thirty-three women taking the drug became infected with HIV, compared to 35 taking the placebo.

The study also showed a much lower rate of adherence to the medication regimen (40 per cent) and a much higher rate of reported side effects such as nausea, vomiting and kidney or liver abnormalities.