By Lizzie van Dorp
Similar to PrEP, Post-exposure prophylaxis (PEP) is antiretroviral medication used to reduce the possible transmission of HIV to a seronegative person. The difference, however, is that the therapy is given after possible infection. PEP must be started as soon as possible within first 72 hours after potential exposure. The full course of the 28-day treatment should be completed then the risk of transmission can be reduced by 80%. 1, 2, 3
PEP and the target population
Any seronegative person or a person who does not know their HIV status could be prescribed PEP within 72 hours of being exposed to HIV. Workplace accidents, such as the infamous needlestick injury, can elicit the need for the post-exposure prophylaxis, as well as needle sharing in PWID. Transmission risk of different types of sexual acts are taken into account when prescribing PEP. This transmission-risk calculation takes into account whether sex was vaginally or anally, receptive or insertive, and whether the status of sexual partner is unknown or the partner is seropositive.4 Transmission risk of both sexual acts and blood-blood contacts such as needlestick accident, PWID and blood transfusion have been discussed in previous blogs. To refresh, between 4 out of 10.000 acts of condomless insertive penile-vaginal intercourse to 138 per 10.000 acts of condomless receptive anal intercourse result in transmission. For skin-deep needlestick injuries this is 23 per 10.000 injuries.5 The World Health Organization (WHO) recommends to check the HIV status of the source whenever possible. However this is not always possible and should be assumed as positive in regions of the world where HIV is highly prevalent and in high risk populations . The exposed individual should also be tested for HIV as the treatment can cause drug resistance to develop in seropositive people.4
Not only blood or genital contact can warrant PEP. Transmission by exposure to several bodily fluids of a possible HIV infected person [blood, breast milk, genital excretions, cerebrospinal (the fluid surrounding the brain), amniotic (the fluid surrounding the baby in the uterus), peritoneal (fluid in the abdominal cavity), synovial (fluid in the joints), pericardial (fluid around the heart) or pleural fluid (around the lungs)] could be prevented if PEP is started. The same is true for transmission route. Besides sexual exposure and injury, splashes of fluid to the eyes, nose or oral cavity as well as consumption parentally (in the gastro-intestinal tract) can cause transmission. Transmission risk should be determined at a clinic.
No worldwide cut-off line for an acceptable risk has been described. PEP is not indicated for people already infected with HIV as the treatment can cause drug resistance to develop. Therefore HIV status should be checked before starting treatment.4 Countries usually have their own guideline for prescribing PEP in high-risk and low-risk groups.6, 7
Is PEP safe to use?
PEP regimens most frequently used are Tenofovir (TDF) combined with either Lamivudine (3TC) or Emtricitabine (FTC). These drugs are also used as the preferred first-line regimen in treating HIV. In three-drug regimens the protease-inhibitors Lopinavir (LPV) or Atazanavir (ATV) can be added.4 Previously a two-drug regimen was prescribed due to fear of resistance if a third drug was added. However, a three-drug regimen is less toxic and better tolerated. The three-drug regimen is sadly not available worldwide, and some countries prefer the two-drug regimen due to the merit of their lower cost.6
In addition to drug resistance PEP has possible side effects which shouldn’t be overlooked. Furthermore, it is important to not use PEP frequently and habitually. If this is the case for the individual, PrEP should be considered instead of PEP. The same side-effects as mentioned in a previous blog on side-effects of ART apply to PEP. The most frequently seen are gastro-intestinal problems and skin-rashes. The most important are lactic acidosis, kidney function problems, hepatitis or liver failure. Before starting treatment function of liver and kidneys should be examined.7
Adherence to therapy
One of the problems of PEP is adherence to therapy. Only 57% of people who started treatment with PEP, completed the entire 28-day course. In victims of sexual assault only 40% complete the treatment. An important way to ensure the completion of the PEP course is to prescribe and give the full treatment to the patient at the first consultation. Prescribing the treatment only partially to ensure a follow-up consult has proven to be counterproductive. Furthermore, the possible exposure to HIV can have psychological effects on individuals and therefore it is vital to ensure that the person accepts what happened and the possible risk of exposure. This has also shown to help complete the course. 4, 7, 9
After starting PEP
When the PEP course is completed, it is important to determine whether it was effective. After the four-week treatment liver function and kidney function tests should be repeated as well as HIV status should be checked. If the HIV status is negative after three and six months after the start of therapy, and safe sex has been practiced, no infection has occurred.7
1 http://www.who.int/hiv/topics/prophylaxis/info/en/
2 https://www.hiv.gov/hiv-basics/hiv-prevention/using-hiv-medication-to-reduce-risk/post-exposure-prophylaxis
3 https://aidsinfo.nih.gov/understanding-hiv-aids/fact-sheets/20/87/post-exposure-prophylaxis--pep-
4 World Health Organization Guidelines on Postexpsoure Prohpylaxis for HIV: Recommendations for a Public Health Approach. COD 2105:60 (Suppl 3).
5 Patel P, Borkowf CB, Brooks JT, Lasry A, Lansky A, Mermin J. Estimating per-act HIV transmission risk: a systematic review. AIDS 2014; 28:1509–19.
6 http://www.aidsmap.com/Side-effects/page/1746577/
7 Sultan B, Benn P, Waters L. Current perspectives in HIV post-exposure prophylaxis. HIV AIDS (Auckl) 2014; 6: 147 – 158.
8 http://www.who.int/hiv/topics/prophylaxis/pep_factsheet_dec2014.pdf
9 https://www.hiv.gov/hiv-basics/hiv-prevention/using-hiv-medication-to-reduce-risk/post-exposure-prophylaxis