HIV Prevention medication - PrEP and PEP Antiretroviral Drug Treatment

Monthly Feature : Post-Exposure Prophylaxis (PEP)

Watch Dr. James Fletcher and Dr. Donn Colby in this video by Adams Love explaining in detail about Post-Exposure Prophylaxis, an antiretroviral drug treatment that is started immediately after someone is exposed to HIV. Learn about PEP efficacy, how soon one should take PEP after posible exposure to HIV, criteria and eligibility for taking PEP, course of medication, side effects and why PEP should not be seen as an alternative to safe sex.

Please scroll down for more information and videos on Pre-Exposure Prophylaxis (PrEP) and Post-Exposure Prophylaxis (PEP).

Adam's Love offers detailed information about PrEP study at Anonymous Clinic, The Thai Red Cross AIDS Research Centre. Men who have sex with men in Bangkok aged 18 or above and practice receptive Anal Sex are invited to join the PrEP study conducted by TRCARC.

Learn more about the efficacy of PrEP use as an HIV prevention method in this video by our expert Dr. Nittaya Phanuphak. For more information contact us at or


What is PrEP?

PrEP is short for PreExposure Prophylaxis and may be part of comprehensive HIV prevention services in which HIV negative people who are at high risk, take antiretroviral medication daily to try to lower their chances of becoming infected with HIV if they are exposed to it. To date, PrEP has only been shown to be effective in men who have men who have sex with men (MSM) and transgendered women who have sex with men. Studies are underway to evaluate whether it is safe and effective in reducing HIV infection among heterosexual men and women as well as injection drug users, but those results are not yet available.

In November 2010, the National Institutes of Health (NIH) announced the results of the iPrEx clinical trial, a large, multi-country research study examining whether a pill used to treat HIV can also help prevent HIV infection. The study found that daily oral use of tenofovir plus emtricitabine (brand name Truvada) provided an average of 44% additional protection to men who have sex with men (MSM) and transgendered women who also received a comprehensive package of prevention services that included monthly HIV testing, condom provision, and management of other sexually transmitted infections.
Studies are underway to evaluate whether it is safe and effective in reducing HIV infection among heterosexual men and women as well as injection drug users. A study evaluating oral Truvada for women was terminated early in April 2011 based on indications of a lack of efficacy. Preliminary results indicated that new HIV cases were equally distributed among the groups of women who received or did not receive Truvada in this study. Results from other studies are not yet available.

CDC is leading national efforts to develop formal Public Health Service guidelines for PrEP. Until those more detailed guidelines are available, CDC has developed interim guidance for physicians electing to provide PrEP for HIV prevention among high risk MSM (see graphic and other materials below). In addition, he US CDC has recently released the following preliminary guidance for PrEP use in the United States and suggested it be targeted to high risk MSM.provides the following initial cautions to MSM who may be interested in PrEP before Public Health Service guidelines are available:
  • To date, PrEP has only been shown to reduce HIV infection among gay and bisexual men, and transgendered women who have sex with men, and there are no data regarding its benefit among heterosexuals or injection drug users.
  • PrEP should only be used among individuals who have been confirmed to be HIV-negative. Initial and regular HIV testing is critical for anyone considering using PrEP.  All individuals considering PrEP must also be evaluated for other health conditions that may impact PrEP use.
  • PrEP should never be seen as the first line of defense against HIV. It was only shown to be partially effective when used in combination with regular HIV testing, condoms, and other proven prevention methods. Men who have sex with menMSM should still:

    ◦    Use condoms correctly and consistently
    ◦    Get tested regularly to know their status and that of their partner(s) for certain
    ◦    Get tested – and treated if needed – for other sexually transmitted infections that can facilitate HIV transmission, such as syphilis and gonorrhea
    ◦    Get information and support to reduce drug use and sexual risk behavior
    ◦    Reduce their number of sexual partners
  • Taking PrEP daily is critical.  The iPrEXis study found that PrEP provided a high level of protection only to those who took the pills regularly; protection was very low among those who did not adhere to the daily regimen well.
  • PrEP must be obtained and used in close collaboration with healthcare providers to ensure regular HIV testing, risk reduction and adherence counseling, and careful safety monitoring.
  • Anyone considering using PrEP should speak with their doctor.
2. PEP

What is PEP?

a) Post -Exposure Prophylaxis (PEP) is antiretroviral drug treatment that is started immediately after someone is exposed to HIV. The aim is to get the drugs inside the body as quick as possible to fight the virus allow a person’s immune system a chance to provide protection against the virus and to prevent HIV from becoming established in someone’s body. In order for Post exposure prophylaxis PEP to have a chance of working the medication drugs needs to be taken as soon as possible, definitely within 72 hours, after possible exposure to HIV. Left any longer and it is thought that the effectiveness of the treatment is severely diminished.

Post exposure prophylaxis (PEP) usually consists of a month long course of two or three different types of the antiretroviral drugs that are also prescribed as treatment for people with HIV. As with most antiretrovirals these can cause side effects such as diarrhea, headaches, nausea/vomiting and fatigue. Some of these side effects can be quite severe and it is estimated that 1 in 5 people give up the treatment before completion. The most common drugs prescribed for Post exposure prophylaxisPEP are tenofovir, emtricitabine (or lamivudine), and efavirenz or lopinavir/ritonavirzidovudine, lamivudine and nelfinavir.

b) Post-Exposure Prophylaxis (PEP) is a course of antiretroviral drugs which is thought to reduce the chance of HIV establishment risk of seroconversion  in one's body after events with high risk of exposure to HIV (e.g., unprotected anal or vaginal sex, or needle-stick injuries, or sharing needles).

To be most effective, one need to begin treatment antiretroviral drugs should begin within an hour of as soon as possible after possible exposure infection, and no longer than 72 hours post-exposure. Prophylactic treatment course for HIV typically lasts four weeks.
While there is compelling data to suggest that PEP after HIV exposure is effective, there have been cases where it has failed. Failure has often been attributed to the delay in receiving treatmentPEP, the level of exposure (i.e., the viral load received), or both. However, for non-occupational exposures, the time and level of exposure are based on patient-supplied information; absolute data is therefore unavailable. PEP can also slow down the development of antibodies, potentially causing false negatives on a later HIV test. Doctors will advise patients who received PEP to get anti-HIVa test at the completion of PEP course and at 3-6 months after that at 6 months post-exposure as well as the standard 3 month test.
The antiretroviral regimen used in PEP requires close compliance and can have unpleasant side effects including malaise, fatigue, diarrhea, headache, nausea and vomiting.

PEP is not a cure for HIV and is not guaranteed to prevent HIV from taking hold once the virus has entered the body. Condoms and lube for sex remain the most efficient way of staying safe from HIV. If You Need Help Deciding If You Need PrEP or PEP, contact Anonymous Clinic