Pre-exposure prophylaxis

Pre-exposure prophylaxis (PrEP) is the preemptive use of drugs to prevent disease in people who have not yet been exposed to the disease-causing agent.

In particular, the term is used to refer to the use of antiviral drugs that attack the lifecycle of the HIV virus as a strategy for the prevention of HIV/AIDS. PrEP is an optional treatment which may be taken by people who are HIV negative, but who have substantial, higher-than-average risk of contracting an HIV infection. Currently, the only drug which any health organization recommends for HIV/AIDS PrEP is Truvada, which is the brand name of the Gilead Sciences drug combination of tenofovir/emtricitabine. The Centers for Disease Control says that "PrEP is a powerful HIV prevention tool and can be combined with condoms and other prevention methods to provide even greater protection than when used alone". However, people who use PrEP must commit to taking the drug every day and seeing their health care provider for follow-up every three months.

Truvada's active ingredients, tenofovir disoproxil (TDF) and emtricitabine (FTC), are nucleotide analog reverse transcriptase inhibitors. TDF and FTC effectively block HIV from incorporating its genetic material into the host's genome, and thus prevents HIV infection. PrEP is intended for use with condoms, so that each method can compensate for essential or casual efficacy deficits of the other.

In the United States, federal guidelines recommend the use of PrEP for HIV negative people with the following characteristics:

The PrEP studies have shown the drugs to be generally safe, with few side effects. Generally, minor side effects such as nausea or diarrhea resolve themselves within the first few months. Any deleterious effect of Truvada on kidney function usually reverses with drug discontinuation, but irreversible kidney damage can rarely occur.

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