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Post-exposure treatment after unsafe sex

A one month course of anti-HIV therapy is now standard treatment for health-care workers who are exposed to HIV during workplace accidents, such as needlestick injuries. However, the use of post-exposure treatment after non-occupational exposures to HIV, such as through unprotected sex, remains controversial. Three new articles published on the Web this week help to illuminate the controversy.

Occupational use

The main evidence for the effectiveness of post-exposure treatment comes from a retrospective analysis of health-care workers, recently published in the New England Journal of Medicine (NEJM). Individuals who took AZT monotherapy for a month were significantly less likely to seroconvert than those who received no post-exposure treatment.

Guidelines on post-exposure treatment for health-care workers have been published by the Centers for Disease Control and Prevention (CDC) in the USA. The recommended regimen now consists of AZT/3TC with additional indinavir in cases of the highest risk. Treatment needs to be started promptly to maximise its chances of success; animal studies suggest that after 48 hours treatment may be ineffective.

Use after sex or drug use

Research is under way into post-exposure treatment of individuals exposed to HIV during sex or injecting drug use; for example, see the online documentation for the San Francisco Feasibility Study.

No formal guidelines currently exist, although possible approaches were discussed in detail in an article by workers involved in the San Francisco study, published in the NEJM in April 1997.

This week, these authors published a new article in the Annals of Internal Medicine, proposing a comprehensive strategy for the care of people with recent sexual exposure to HIV. A table summarises the scenarios in which they recommend post-exposure treatment.

Effects on behavior?

However, sceptics have suggested that post-exposure treatment could do more harm than good. They point out that there is no hard evidence that it works in non-occupational settings, and voice concern that the availability of a so-called 'morning after' treatment for HIV, along with more effective treatments for infected people, might lead to an increase in unsafe behaviors. For more information on these concerns, see the article Protease Dis-Inhibitors? at HIV InSite.

However, large-scale British research published in full on the Web this week does not support the notion that improvements in the medical treatment of HIV has led to changes in gay men's sexual behavior. No increase in unprotected anal sex was observed between 1994 and 1997, and few respondents reported that medical progress meant that they were more likely to take risks.

The San Francisco researchers have argued that they only support post-exposure treatment as part of a comprehensive program of HIV prevention work. Individuals who come forward after possible exposure to HIV are a high priority group for interventions designed to help them avoid such risks in the future.

Continuing consultation

In July 1997 the CDC convened a meeting to discuss whether it should draw up recommendations on non-occupational post-exposure treatment, and this week it published a factsheet summarizing the conclusions. The document describes post-exposure treatment as "a complicated medical therapy that should never be considered a desirable form of primary HIV prevention", and concludes:

"CDC affirms that efficacy data and additional epidemiological information are needed (e.g., the number of infections that could be averted by antiretroviral drugs, the number of people who would need to be treated to avert one infection, effects of antiretroviral drug availability on risk behavior, physician practices in prescribing antiretroviral drugs) before public policy recommendations can be formulated. Many more questions have been raised and many experts at the meeting urged that caution should be used in future decision making until more data are available. A PHS Working Group will deliberate on the proceedings and develop a statement for public comment later in 1998. Currently, the use of antiretroviral drugs for non-occupational exposures to HIV should be considered a clinical intervention of unproven efficacy. Individual practitioners and their patients may opt to consider its use in specific circumstances following exposures to HIV that carry a particularly high risk of infection, but only after careful consideration of the potential risks and benefits and with a full awareness of the many gaps in our current knowledge."