Health care workers who are occupationally exposed to human immunodeficiency virus (HIV) should receive postexposure chemo-prophylaxis. Henderson reviews the recently revised U. S. Public Health Service guidelines for chemoprophylaxis, issued in 1998. The concerns about giving chemoprophylaxis to healthy people revolve around the potential toxicity of the agents used and the fact that, for ethical reasons, clinical trials cannot be done to prove the efficacy of antiretroviral agents used for postexposure prophylaxis. Almost all agents used have had serious adverse effects, such as bone marrow suppression, peripheral neuropathy, nephrolithiasis and hepatocellu-lar injury. However, there are no reports of long-term sequelae, even in those who have had serious adverse effects. Dose reduction of the chemoprophylactic medication and treatment of adverse effects have enabled exposed workers to be more compliant with the regimen. The proposed regimens are based in part on animal and human studies. The relevant human studies primarily involve reduction of vertical transmission (between mother and neonate) accomplished with administration of zidovudine before birth and during labor and delivery, and then to the baby after birth. This led to a two-thirds reduction in HIV transmission. Even zidovudine begun in the first 48 hours after birth (a similar scenario to an exposed health care worker) led to a reduced risk of HIV transmission. Zidovudine is the only agent about which there is any data about postexposure efficacy.

The major risk factors for occupational HIV infection are: (1) deep injury, (2) visible blood on the injuring device, (3) injury with a needle that had been in the infected patient's blood vessel, (4) terminal illness in the infected patient and (5) less likelihood of taking zidovudine postexposure chemopro-phylaxis. The new guidelines use these risk factors to some extent in determining the drug regimen that should be followed (see table). The exposure site should be washed with soap and water as soon as possible after the exposure, and then cleaned with sterile saline or a disinfectant solution. Thorough irrigation should occur if the exposed area is a mucous membrane. Postexposure anti-retroviral chemoprophylaxis should be offered to all exposed health care workers, even those who are pregnant. Ideally, the first dose will be given within one hour of exposure. If drug resistance is a possibility, it may be wise to add an agent that the source patient has not received. Although the guidelines call for a “basic” regimen and an “expanded” regimen (to be used in those whose HIV exposure is thought to be greater), Henderson states that his institution offers the “expand- ed” (three-drug) regimen to exposed health care workers more often than these guidelines suggest. The argument is that offering a presumably “less effective” regimen is untenable.