Post-Exposure Prophylaxis (PEP) for Sexual Exposures

Post-exposure prophylaxis (PEP) is a type of antiviral therapy for HIV designed to reduce (but not eliminate) the possibility of infection with the virus after a known exposure. Currently, PEP is primarily intended for the prevention of infection in cases where there has been a known high-risk work-related (occupational) exposure to HIV. For more information on the management of PEP for occupational exposures, please read the following published guidelines:

"Public Health Service Guidelines for the Management of Health-Care Worker Exposures to HIV and Recommendations for Postexposure Prophylaxis," Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention, May 15, 1998, Vol. 47 #RR-7. (This is a PDF.)

Unlike PEP for occupational exposures, there is very little data on the effectiveness of PEP for sexual exposures, nor are there any formal guidelines from the CDC on this issue.

The following reviews some preliminary information regarding PEP after sexual exposures. I will discuss circumstances when PEP may be considered, and when PEP is not recommended. These suggestions are subject to change, as further information becomes available. One paper on this issue that has already been published in the medical literature is:

"The Care of Persons with Recent Sexual Exposure to HIV," Annals of Internal Medicine, Katz, M.H. and Gerberding, J.L., 15 February, 1998, Vol. 128, pages 306-312.

Based on currently available information, PEP may be considered after a sexual exposure if all of the following criteria are met:

  1. A person has had a known high-risk exposure to HIV, AND

  2. The person was exposed to another person who is known to have HIV (especially if they have a high viral load), or the other person is known to be at very high risk for HIV, AND

  3. The exposure is an isolated incident and future exposures are very unlikely, AND

  4. The person is compliant with taking their medications, AND

  5. Antiviral medications are not contraindicated in their case (not all people can take these medications), AND

  6. Treatment begins preferably within several hours after the high-risk exposure, or if necessary, up to 24-36 hours after the high-risk exposure. The benefits of beginning treatment beyond 36 hours are not known. PEP usually involves sustained treatment, for approximately four weeks.

PEP may also be considered in situations such as rape, if there is a significant risk of infection, depending upon the specific circumstances.

However, there are circumstances when PEP is not recommended after a sexual encounter.

  1. PEP is not recommended for treating people who have had low-risk exposures to HIV (for example, receiving oral sex, kissing, protected sex, mutual masturbation, etc.).

  2. PEP is not recommended for treating people who have had exposures to a person whose HIV status is unknown, or whose risk factors are unknown.

  3. PEP is not recommended for treating people who intend to use PEP as a way to maintain high-risk activities while reducing their risk for HIV.

  4. PEP is not recommended for treating people who are using PEP as a way to avoid getting tested for HIV.

  5. PEP is not recommended merely to give people "peace of mind."

PEP is meant to reduce the possibility of becoming infected with HIV after a known exposure. It is not designed to do any of the following things:

  1. PEP will not eliminate the need to be tested for HIV over the next six months.

  2. PEP will not eliminate the need to use condoms with all of your sexual partners over the next six months.

  3. PEP will not prevent infection with other STDs.

  4. PEP will not guarantee that you will not get infected with HIV.

  5. PEP will not prevent future infections with HIV.

  6. PEP will not solve issues such as fear, guilt, paranoia and similar emotions, and is not recommended for such purposes!

PEP involves much more than just taking a few pills every day. In addition to properly taking antiviral medications (and dealing with drug side effects), PEP also involves in-depth risk-reduction counseling. This includes taking actions to avoid high-risk activities in the future, and also includes learning about the correct use of condoms. Also, testing for other STDs, such as chlamydia, gonorrhea, syphilis and hepatitis B, is important, since HIV antiviral drugs will not prevent infection with other STDs. This is also a good opportunity to begin hepatitis B vaccination, if necessary.

We have a lot of good information about the effectiveness of PEP after occupational exposures, and very good treatment guidelines for drug therapy after occupational exposures to HIV. However, the same cannot be said of PEP after sexual exposures. There are no established guidelines regarding which drugs to use when PEP is considered for sexual exposures. Katz and Gerberding have published some suggestions regarding which drugs to use under these circumstances (see above), but these suggested treatments are subject to change as time progresses.

These drugs have to be taken exactly as prescribed. If they are not taken exactly as prescribed, drug resistance can occur. It is also important that these drugs only be prescribed by doctors who have experience with and knowledge of these drugs, otherwise they may not be aware of all the side effects, contraindications, drug interactions, etc., that are frequently seen with HIV antiviral medications.

These drugs are not candy! They should not be prescribed just to give a person peace of mind. They should only be prescribed when treatment with these drugs is clinically indicated. These are powerful drugs and must be taken following strict dosing guidelines; side effects are very common, and can sometimes be very serious.

These drugs are also extremely expensive (especially the protease inhibitors). Taking these drugs unnecessarily can easily raise health-care costs needlessly (even if you pay for the drugs yourself). Like it or not, we have to carefully look at health-care costs to prevent further rationing of medical care in the future. In addition, PEP requires that these drugs be started within a few hours (or at most 24-36 hours) after a known high-risk exposure; yet many of these drugs are not readily available in most pharmacies. Therefore PEP is not available to most people under most circumstances.


PEP is much more than merely taking a few pills every day. If you want to take these drugs because you are asking yourself, "But what if this person has the virus? But what if there was blood in their saliva? But what if . . .?" then most likely, taking these drugs is not indicated in your case. At this time, the benefits of taking these medications after a sexual exposure are still being investigated, and there is still very little information regarding the use of these drugs in such cases. If you have had a high-risk exposure to a person known to have HIV (especially if they have a high viral load), then you will need to talk to a doctor knowledgeable about HIV antiviral medication immediately after the high-risk exposure. The doctor must then decide if PEP may be helpful under your circumstances, and which drugs to prescribe.

My suggestion to everyone is to take steps now to reduce your risk (reducing the number of your sexual partners, practicing safer sex, correctly using condoms, etc.), rather than relying on PEP to stay HIV negative. If you are dealing with issues such as fear, guilt and similar emotions, then I strongly suggest you seek mental-health counseling, rather than requesting PEP treatment from your doctor.

Do you want more information on AIDS, STDs or safer sex? Contact the U.S. Centers for Disease Control AIDS hotline, open 24 hours a day, seven days a week, at 1-800-CDC-INFO. Or visit The Body's Safe Sex and Prevention Forum.

Until next time . . . Work hard, play hard, play safe, stay sober!