Understanding PrEP and Truvada

A few weeks ago, both the World Health Organization and the US Food and Drug Administration announced that they were endorsing the use of Truvada, an ARV developed by Gilead, as the first PrEP (pre-exposure prophylaxis) for people at high risk of HIV. Which is leaving many [eople with questions about what is PrEP, how will it work and who needs it.

What is PrEP?

Prophylaxis is a medical term for preventing something. In this case, the idea is to prevent people from being infected with HIV. The focus of PrEP is on people who are at risk of getting HIV, specifically men who have sex with men and people who are HIV negative and married to someone who is HIV positive. Protecting these high risk groups from getting infected will significantly cut down on the number of new HIV infections both now and in the future.

Pre-exposure means before someone is exposed to the infection. So PrEP is trying to protect people against HIV before they are exposed to it. This is different from condoms, which provide protection when the exposure happens.

How Does PrEP Work?

The idea behind PrEP is that if a person who might be exposed to HIV is already on ARVs, then even if the virus gets into their body, it won't be able to infect them, because the ARV will keep the virus from making copies of itself and spreading through the body.

For a long time, no one was sure if PrEP would actually work. However studies found that people at high risk of HIV infection who started taking Truvada were less likely to be infected than people who were not taking Truvada. The studies were successful enough to convince WHO and the FDA to endorse the use of Truvada as PrEP.

Image by Jeffery Beale, CC3.0

Criticisms and Drawbacks

There have been a number of concerns about the use of Truvada as PrEP. Some of these concens have been addressed by the clinical trials, but some remain.

  • Cost of PrEP: In the US Truvada costs $14,000 per year. Generics in other countries are less expensive, as low as $8 a month. However money for HAART for people with HIV is already hard to come by. Should money be put torwards paying for PrEP when it could be put to treating people who are already sick? Luckily, this may not be as big an issue as it seems – a cost effectiveness analysis of the clinical trials for Truvada as PrEP found that South Africa would save money over all by implementing PrEP over the next five years. Hopefully other countries might have similar benefits.
  • Resource Cost: In South Africa and many other counties, Truvada is one of the main ARVs. Using it to as a PrEP will leave less medicine available for people who are sick.
  • Increased Risk Taking: Some experts have expressed concern that people on PrEP might assume that they cannot get HIV while on PrEP (which is false) and take more risks such as not using condoms, thus actually increasing the spread of HIV. The one study that tracked condom use found that the people on PrEP were more likely to use condoms, but we don’t know yet if this will be universal or is just an oddity in one study.
  • Drug Resistance: If people on PrEP do not take it the way they are supposed to, they will not have the protection against HIV. At the same time, if they get infected it is more likely that the virus will develop a resistance to Truvada. Drug resistant strains of HIV are already a concern and no one wants to see more develop.

Usage Recommendations

Currently Truvada is approved for use as an HIV preventative for groups as high risk of HIV/AIDS. However there are not yet clear guidelines for doctors in how to prescribe it and what instructions to give to high-risk patients who take Truvada.

Both the FDA and WHO are working on developing usage recommendations. Currently the Us Center for Disease Control is providing interim guidelines for US physicians while more permanent guidelines are being developed. The CDCs interim guidelines for Truvada as PrEP are available online.

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