Pre-exposure prophylaxis is any medical or public health procedure used before exposure to the disease causing agent, its purpose is to prevent, rather than treat or cure a disease. An example would be if a doctor gave a medication used to treat a disease to a healthy person who is not thought to have that disease, but is at risk for contracting it. More specifically, this practice is common with people who are about to travel from an area without malaria to an area where malaria is a risk. It is also commonly used as a tool to prevent persons from contracting HIV, as is recommended by the CDC.
Pre-exposure prophylaxis for malaria
Some of the factors in deciding whether to use chemotherapy as malaria pre-exposure prophylaxis include the specific itinerary, length of trip, cost of drug, previous adverse reactions to antimalarials, drug allergies, and current medical history.
Pre-exposure prophylaxis for HIV (PrEP)
The terms "pre-exposure prophylaxis" or "PrEP" most commonly refer to an HIV-prevention strategy where antiretrovirals are used to protect HIV-negative people from HIV infection. The HIV antiviral Truvada was approved by the FDA for PrEP on July 16, 2012. The CDC amended its guidelines for HIV prevention recommending pre-exposure prophylaxis with Truvada to high infection risk populations on May 14, 2014,  due to research indicating prophylactic effectivity preventing transmission from mother to child. Prior to that date, Truvada was only approved to treat existing HIV infections.
Most PrEP studies utilize the drug tenofovir or a tenofovir/emtricitabine combo (Truvada) that is delivered orally. Initial studies of PrEP strategies in non-human primates showed a reduced risk of infection among animals that receive ARVs prior to exposure to a simian form of HIV. A 2007 study at UT-Southwestern (Dallas) and the University of Minnesota showed PrEP to be effective in "humanized" laboratory mice. In 2008, the iPrEx study demonstrated 42% reduction of HIV infection among men who have sex with men, and subsequent study of the data indicated 99% protection with daily adherence.
|Study||Type of PrEP||Study Population||Findings|
|CAPRISA 004||Pericoital tenofovir gel||South African females||39% reduction of HIV infection|
|iPrEx||Oral emtricitabine/tenofovir||Men who have sex with men||42% reduction of HIV infection. 99% reduction estimated with daily adherence|
|Partners PrEP||Oral emtricitabine/tenofovir; oral tenofovir||African heterosexual couples||73% and 62% reduction of infection|
|TDF2||Oral emtricitabine/tenofovir||Botswana heterosexual couples||63% reduction of infection|
|FEM-PrEP||Oral emtricitabine/tenofovir||African females||No reduction (study halted due to low adherence)|
|VOICE 003||Oral emtricitabine/tenofovir; oral tenofovir; vaginal tenofovir gel||African females||No reduction in oral tenofovir or vaginal gel arms [oral emtricitabine/tenofovir arm ongoing]|
|Bangkok Tenofovir Study||Oral tenofovir||Thai male injection drug users||48,9% reduction of infection|
The PrEP studies have shown the drugs to be safe, with few side effects. Generally, minor side effects such as nausea or diarrhea resolve themselves within the first few months. Effects of Truvada on kidney function have been shown to be temporary.
- Kathrine R. Tan, Sonja Mali, Paul M. Arguin (2010). "Malaria Risk Information and Prophylaxis, by Country". Travelers' Health - Yellow Book. Centers for Disease Control and Prevention. Retrieved 20 December 2010.
- Celum C, Baeten JM (February 2012). "Tenofovir-based pre-exposure prophylaxis for HIV prevention: evolving evidence". Curr. Opin. Infect. Dis. 25 (1): 51–7. doi:10.1097/QCO.0b013e32834ef5ef. PMC 3266126. PMID 22156901.
- Denton PW, Estes JD, Sun Z, et al. (January 2008). "Antiretroviral pre-exposure prophylaxis prevents vaginal transmission of HIV-1 in humanized BLT mice". PLoS Med. 5 (1): e16. doi:10.1371/journal.pmed.0050016. PMC 2194746. PMID 18198941.
- Grant RM, Lama JR, Anderson PL, et al. (December 2010). "Preexposure chemoprophylaxis for HIV prevention in men who have sex with men". N. Engl. J. Med. 363 (27): 2587–99. doi:10.1056/NEJMoa1011205. PMC 3079639. PMID 21091279.
- Andrei G, Lisco A, Vanpouille C, et al. (October 2011). "Topical tenofovir, a microbicide effective against HIV, inhibits herpes simplex virus-2 replication". Cell Host Microbe 10 (4): 379–89. doi:10.1016/j.chom.2011.08.015. PMC 3201796. PMID 22018238.
- Celum, CL (December 2011). "HIV preexposure prophylaxis: new data and potential use.". Topics in antiviral medicine 19 (5): 181–5. PMID 22298887.
- Choopanya K, Martin M, et al. (June 2013). "Antiretroviral prophylaxis for HIV infection in injecting drug users in Bangkok, Thailand (the Bangkok Tenofovir Study): a randomised, double-blind, placebo-controlled phase 3 trial". The Lancet 381 (9883): 2083–2090. doi:10.1016/S0140-6736(13)61127-7. PMID 23769234.
- PrEPWatch PrEP Watch homepage
- Singh JA, Mills EJ (2005) The Abandoned Trials of Pre-Exposure Prophylaxis for HIV: What Went Wrong? PLoS Med. 2(9): e234
- Lange J (2005) We Must Not Let Protestors Derail Trials of Pre-Exposure Prophylaxis for HIV PLoS Med. 2(9): e248.
- Aidsmap.com: Nevirapine studied as pre-exposure prophylaxis for HIV: safe in 200 mg dose
- Aidsmap.com: Pre-exposure prophylaxis may only offer limited benefit
- CDC: CDC Pre-Exposure Prophylaxis (PrEP)