Nearly 100 percent of new adult infections of human immunodeficiency virus (HIV) result from sexual or intravenous drug contacts. Nonoccupational HIV postexposure prophylaxis (PEP) is being used in some areas, and physicians are being asked by patients to provide PEP. Merchant discusses nonoccupational HIV PEP in the emergency department and makes recommendations for its use.

The Public Health Service (PHS) has issued guidelines for occupational PEP, primarily for exposure occurring through needle stick of a health care worker. Early prophylactic recommendations for nonoccupational HIV exposure included the use of vinegar douches and nonoxynol-9. Zidovudine was also considered to have some beneficial prophylactic effects based on limited occupational PEP studies and studies in exposed neonates. In support of zidovudine as a prophylactic, in 1997 and 1998 two experts, Dr. Julie Gerberding and Dr. Mitchell Katz, recommended the development of nonoccupational PEP guidelines, and in 1998 the PHS acknowledged the potential value of PEP but emphasized that it cannot replace primary prevention. Nevirapine has recently demonstrated even greater efficacy than zidovudine in reducing perinatal HIV transmission.

The probable time lag between exposure to HIV and the time human cells become infected presumably allows an opportunity for prophylaxis. Early chemoprophylaxis with anti-retroviral medications may halt HIV replication, allowing the body to destroy the virus using regular immune mechanisms. The timing of initiation of prophylaxis appears to be critical. The optimal window for PEP is 24 to 48 hours after exposure; prophylaxis initiated beyond 72 hours is probably ineffective. Guidelines for who should be offered PEP vary, with Katz and Gerberding recommending PEP (1) after high-risk exposure, (2) after exposure to a sex partner who is known to be infected with HIV or belongs to an HIV risk group, (3) if the exposure is isolated and (4) if the exposure occurred within 72 hours.

The PHS guidelines for nonoccupational PEP consider (1) the risk of HIV transmission (e.g., the HIV status of the source), (2) the type and risk assessment of the method of exposure (e.g., unprotected sex, type of sex activity) and (3) any factors that might affect the risk from exposure (e.g., mucosal tears, presence of a sexually transmitted disease [STD]). The latter guidelines advise that treatment may be most effective within one to two hours of exposure and no later than 36 hours.

The optimal regimen for nonoccupational HIV PEP is unknown. Katz and Gerberding have proposed a detailed guideline for drug choice. Given that the details surrounding an exposure are often unclear, the regimen proposed in the accompanying table provides an initial three-drug antiretroviral treatment that can be modified during follow-up if appropriate. The PHS has developed a registry for patients prescribed nonoccupational HIV PEP (toll-free telephone number: 877-HIV-1PEP [877-448-1737]) to gather additional information.

The author concludes that although the provision of nonoccupational PEP is controversial, rapid response is necessary for evaluation and management of HIV PEP and is an appropriate emergency department activity. After early initiation of prophylactic medications, follow-up should include (1) reevaluation of the patient's need for PEP, (2) modification of medications if appropriate, (3) HIV testing, (4) appropriate laboratory testing, (5) HIV and STD counseling, (6) monitoring of PEP medication effects, (7) further counseling and instruction regarding PEP and (8) attention to any special situation (e.g., aftermath of sexual assault). Patients require PEP treatment and follow-up weekly for at least four weeks to stress compliance and offer further counseling about safer sex practices. Patients must understand that the efficacy of PEP is unknown and that PEP does not prevent further HIV infection.