“PEP Talk”: Post-Exposure Prophylaxis


There are a couple reasons why I’ve decided to write a post on post-exposure prophylaxis. First, there’s a proposed bill in the BC legislature (link to the bill itself here) which is worrying because it would force testing for HIV in people whose body fluids emergency workers come into contact with. Post-exposure prophylaxis (PEP) is sometimes used in extreme cases of risky exposures of healthcare workers. Second, I was at the BC Centre for Excellence in HIV/AIDS Antiretroviral Update today and saw a nice talk by Dr. Val Montessori on PEP, which I’ll try to summarize here.

What is PEP?

Post-exposure prophylaxis is the use of HIV drugs to prevent infection after someone has been exposed to HIV. Generally, we think of PEP as proceeding after a healthcare worker has accidentally stuck themselves with a needle used on an HIV-positive individual (a needlestick injury).

For PEP, HIV antiretroviral drugs are given to the healthcare worker as soon as possible after the exposure (generally within 72 hours). The drugs can stop HIV infection from happening by blocking the replication of the virus itself. If the medications are given soon enough, they can work to limit the ability of HIV to make enough copies of itself to actually establish an infection in the person taking PEP.

In BC, most emergency rooms will have a “starter kit” of PEP medications. These drugs target the protease and reverse transcriptase proteins of HIV, preventing the virus from replicating.

There are 3 drugs that most people in BC will receive for PEP currently.  Two are NRTIs (drugs that look like DNA building blocks that HIV accidentally puts into its own DNA, which breaks the chain of DNA as it is being built). The NRTIs are called tenofovir and lamivudine. The third drug is a PI, and is actually a combination of two drugs with the trade name Kaletra. One of these drugs works against the HIV protease protein, and by blocking protease, it prevents new baby viruses from maturing into fully infectious viruses (this drug is called lopinivir). The other component of Kaletra is called ritonavir. It “boosts” the levels of lopinivir in the blood by basically slowing the breaking down of lopinivir in the liver.

Basically, these drugs work exactly the same in someone taking PEP as they do in someone who has HIV, but block infection in someone taking PEP because of the very small numbers of viruses that are around at the beginning of infection compared to someone who has been infected for longer.

Things to remember

The first question that needs to be answered before using PEP is whether there has actually been an exposure. PEP is only necessary when there is a real risk of HIV infection. In other words, a needlestick from someone who is HIV negative is clearly not a risk for transmitting HIV. The nature of the exposure is also important. For example, an exposure to HIV-positive blood through a needlestick has a higher risk of transmission than exposure simply by contact on skin. There have been no documented cases of HIV transmission through contact with HIV-positive body fluid on unbroken skin like would occur from a blood splash. The type of body fluid that someone is exposed to is also important. Blood, genital fluids, and internal fluids like those from internal organs are riskier fluids than others because they contain higher levels of HIV. Some body fluids that are not infectious are spit, urine, tears or sweat.

Another thing to remember is that even getting a needlestick from a person who is known to be HIV-positive has a pretty low risk of transmission of about 0.3% (1 in 300). This risk falls even further when the HIV status of the reference individual (the person whose body fluids were involved) is unknown.

There are also a number of side effects associated with taking antiretroviral medications, and the risk associated with PEP may outweigh the risk of infection.

Sometimes PEP just isn’t the right choice for many situations. A potential exposure to an infectious agent like HIV can be very worrisome for people. Some people may request PEP for situations where HIV transmission is extremely unlikely, such as stepping on a needle in public or contact with non-infectious body fluid. The BC Guidelines for Post Exposure Prophylaxis say that PEP is not the right choice in cases where the risk of infection is low. The guidelines say that the “treatment of a high anxiety level in the exposed person is reassurance counseling and education. It is not antiretroviral therapy”.

This is why the bill I mentioned before is concerning. First, the risk involved in even the most extreme case of exposure (a needlestick from a known HIV-positive person) is quite low. Second, the bill is quite vague as to what it considers “body fluids” (would sweat be included?). Third, the bill does not specify what “contact” would be considered significant, leaving some speculation that even a splash could be considered “contact” (even though there have not been any documented cases of HIV transmission by contact with unbroken skin).

There is also very serious concern over the violation of rights that are involved in forcing people to get tested with HIV. The BC Guidelines on PEP clearly state that people need to give permission to have an HIV test.  Forcing people to get tested for HIV would violate rights that are held in the Canadian Charter of Rights and Freedoms. These include the right to privacy and the right to bodily integrity. Furthermore, the knowledge that someone could be forced to get tested for HIV could make them less likely to call for help or engage with healthcare in an emergency.

Instead of making laws that violate the rights of citizens and which are not based in sound evidence, there should instead be better education of the public and emergency workers on what is real risk for HIV transmission and what is not.

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Comments
2 Responses to ““PEP Talk”: Post-Exposure Prophylaxis”
  1. Billy says:

    I liked the overview, but I feel like you left out the cases where pep was denied to people who requested it after an exposure during sex with a positive person. There was an implication that granting access to the treatment was extremely discretionary. I recall that there were cases that were seemingly perfect fits for the treatment, it was denied, and the person was infected.

    I personally think that this aspect is as interesting/concerning as issues of right to privacy with the new legislation.

  2. Andrea says:

    We have heard of people having this experience in Victoria, on Vancouver Island – where they present to the hospital and are not given access to PEP. There is clearly advocacy needed within the health profession as to adhering to guidelines which would give access to PEP for people who have had risky sex with a positive person.

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