HUMAN IMMUNODEFICIENCY VIRUS (HIV)

Risk of transmission after percutaneous (through the skin) exposure to HIV-infected blood is approximately 0.3%, and after a mucous membrane exposure is approximately 0.09%. The more blood one is exposed to, the greater the risk. An appropriate medical provider should evaluate within hours any person exposed to HIV.

Post Exposure Prophylaxis (PEP) for HIV

Most occupational exposures to HIV do not result in the transmission of HIV. Thus, the potential toxicity of PEP must be carefully considered in the risk: benefit evaluation for treatment. Approximately 50 % of patients experience some side effects, which include, but are not limited to: nausea, fatigue, headache, lack of appetite and skin problems. In up to 33 % of cases, the symptoms may be severe enough that PEP is halted. There are potentially also some very serious life-threatening effects that people should appreciate, especially because the exposed patient being treated may in fact not be infected with HIV.

Biological plausibility supports the argument that infection can be prevented or ameliorated by using antiretroviral drugs. Systemic (whole body) infection with HIV does not occur immediately, leaving a brief window of opportunity during which postexposure antiretroviral intervention might modify or prevent viral replication. In theory, early PEP may limit the proliferation of virus in the initial target cells or lymph nodes.

There is evidence that specific agents currently used for prophylaxis are efficacious. Animal studies have inherent problems of extrapolating to human response. Still, animal studies have shown that larger viral doses on exposure decreased the efficacy of prophylaxis. Furthermore, delaying initiation, shortening the duration, or decreasing the antiretroviral dose of PEP, individually or in combination, decreased prophylactic efficacy. In one human study, ZDV alone was associated with a reduction in the risk of HIV infection by approximately 81%.

In some cases, PEP may fail in preventing HIV infection. Reasons for apparent failure include, but are not limited to: exposure to a strain of HIV that is resistant to the specific medication given; exposure to a high titer of virus or large amount of blood; delay in initiation of PEP or inadequate duration of PEP.

If the decision to treat had been made, PEP should be initiated as soon as possible - ideally within an hour of exposure. Still, the interval after which no benefit is gained from PEP for humans is undefined. Therefore, if appropriate, PEP should be started even after 36 hours. If the source of exposure is determined to be HIV negative, PEP should be discontinued. The typical duration of PEP for HIV is 4 weeks long.

There are three classes of antiretroviral agents that are used in the treatment of HIV infection. All work by trying to inhibit the replication of new virus from being formed and infecting new cells. These include: nucleoside reverse transcriptase inhibitors (NRTIs), nonnucleoside reverse transcriptase inhibitors (NNRTIs,) and protease inhibitors (PIs.) A physician, knowledgeable in the area of HIV/AIDS should make the actual choice of medication, with the concordance of the patient.

The emotional aspect of an exposure to HIV may be substantial, and should not be ignored. Thus, access to providers knowledgeable about occupational HIV transmission and who can deal with the many concerns an HIV exposure might generate for the exposed person is an important element of post-exposure management.

Specific recommendations to HIV exposure should include measures to prevent secondary transmission - the transmission of the virus from the exposed individual to others. These recommendations are important especially during the first 6-12 weeks post-exposure, a time period during which most HIV-infected individuals will convert to HIV+. The recommendations include: sexual abstinence or the use of condoms; refraining from donating blood, plasma, organs, tissue or semen.

Things to remember:

• In the case of any acute illness following exposure, the affected individual should consult a physician.
• Knowledge about the efficacy of drugs used for PEP is limited
• Combination drug regimens are often used because of increased effectiveness and concerns about drug-resistant viruses
• Data regarding toxicity of antiretroviral drugs in persons without HIV infection are limited
• Serious adverse events have occurred in persons taking PEP
• Any or all drugs for PEP may be declined or stopped by the exposed person

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(The above reflects information from: Updated U.S. Public Health Service Guidelines for the Management of Occupational Exposures to HBV, HCV, and HIV and Recommendations for Postexposure Prophylaxis Vol 50, No RR11;1 06/29/2001)

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