less to beginning treatment are eligible for post-exposure prophylaxis. If the exposure occurred over 73 hours prior to treatment initiation, post-exposure prophylaxis is not indicated. Testing Initial HIV testing: Before initiating PEP after potential HIV exposure, persons should be tested for HIV1 and HIV2 antigens and antibodies in the blood using a rapid diagnostic test. PEP should only be started if rapid diagnostic test reveals no HIV infection present or if tests results are not available. However, if HIV infection is already present then PEP should not be started. HIV test should be repeated four to six weeks and three months after exposure. People may experience signs and symptoms of acute HIV infection, including fever, fatigue, myalgia, and skin rash, while taking PEP. CDC recommends seeking medical attention for evaluation if these signs and symptoms occur during or after the month of PEP. If follow-up laboratory antibody tests reveal HIV infection, HIV treatment specialists should be sought out and PEP should not be discontinued until person is evaluated and treatment plan is established. STI and HBV testing: People with potential exposure to HIV are also at risk of acquiring STI and HBV. Centers for Disease Control and Prevention (CDC) recommends STI-specific nucleic acid amplification testing (NAAT) for gonorrhea and chlamydia and blood tests for syphilis. PEP is also active against HBV infections so discontinuation of medication can cause the reactivation of HBV, though rare. Health care providers must monitor HBV status closely. Follow up testing: Serum creatinine and estimated creatinine clearance should be measured at baseline to determine the most appropriate PEP antiretroviral regimen. While on PEP, liver function, renal function, and hematologic parameters should be monitored. Treatment In the case of HIV exposure, post-exposure prophylaxis (PEP) is a course of antiretroviral drugs which reduces the risk of seroconversion after events with high risk of exposure to HIV (e.g., unprotected anal or vaginal sex, needlestick injuries, or sharing needles). The CDC recommends PEP for any HIV-negative person who has recently been exposed to HIV for any reason. To be most effective, treatment should begin within an hour of exposure. After 72 hours PEP is much less effective, and may not be effective at all. Prophylactic treatment 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