PEP is not the right choice for people who may be exposed to HIV frequently—for example, if you often have sex without a condom with a partner who is HIV-positive. Because PEP is given after a potential exposure to HIV, more drugs and higher doses are needed to block infection. 

PEP should not be confused with Pre-Exposure Prophylaxis (PrEP), which involves taking medicine on an ongoing basis, before possible exposure to HIV.