Although preventing exposure to HIV remains paramount, evidence suggests that where significant exposure occurs then prompt treatment with combinations of antiretroviral drugs decreases the risk of HIV seroconversion. Although unproven, the presumed mechanism for HIV PEP is that shortly after an exposure to HIV a window period exists. If antiretroviral medications are given they may help to diminish or end viral replication. No definitive data exist on the efficacy of PEP following exposure to HIV other than for occupational exposure. Studies on people with occupational exposure to HIV and animal studies have, however, shown that PEP is effective if commenced as soon as the person is exposed. If there is a delay before the exposed patient presents for PEP, it is usual practice to offer PEP up to 72 hours after exposure. However, its efficacy is likely to fall with increasing delay.
The clinician should make a risk assessment urgently. If the patient is deemed suitable for PEP a senior doctor must assess them as soon as possible. The rationale for PEP varies from clinic to clinic, and it is good practice to have a local clinic protocol for PEP. Further information about PEP can be obtained from BASHH and BHIVA (Walsh & Weston, 2005).
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