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Guidelines For Postexposure Treatment For HIV Under Development At CDC
Atlanta, Georgia, July 25, 1997
In a meeting between agency personnel and external consultants, the Centers for Disease Control and Prevention (CDC) took the first step toward formulating recommendations on postexposure treatment for HIV. However, the CDC will continue to warn that prevention is still the best strategy for avoiding AIDS. The possibility that postexposure therapy may prevent some individuals from getting HIV is exciting, but it in no way changes the CDC's recommendations on prevention.
The CDC began working on guidelines for postexposure treatment after numerous inquiries from healthcare workers in recent years. While the idea of postexposure treatment for HIV was at first limited to treatment of healthcare workers who had been occupationally exposed to the virus, its use has now spread to the general public. Some physicians are now prescribing postexposure treatment on a regular basis to patients who have been raped.
Postexposure treatment is not a primary prevention strategy. The CDC's recommendations have not changed. There is no expection that postexposure treatment will have a major impact on the epidemic in the United States. Only isolated cases will be candidates for postexposure treatment, and that in some cases postexposure treatment will not be effective.
Data on the efficacy of postexposure treatment is limited, according to CDC officials, but a several human studies have demonstrated that postexposure treatment can markedly reduce the risk for contracting HIV in some cases. A 1995 study involving healthcare workers in United States, France and the United Kingdom showed that the use of AZT cuts the risk for HIV infection by 79% following percutaneous exposure to infected blood.
But most of the data on postexposure treatment comes from animal models, and the message coming out of those studies is that there's no such thing as a "morning after" pill for HIV, CDC experts said. Studies show that animals successfully treated postexposure were given anti-HIV drugs early and for several weeks.
Dr. Roberta Black of the National Institute for Allergy and Infectious Disease cited results from one study that showed the experimental acyclic nucleotide analog PMPA has protected some nonhuman primates from infection for more than a year now, after it was given within 24 hours of exposure and administered for four weeks. Studies suggest that animals treated for lesser periods of time are more likely to become infected.
The reverse transcriptase inhibitor nevirapine apparently aborted HIV infection in chimpanzees, according to Dr. Peter Grob of Boehringer Ingelheim. Chimpanzees treated with a loading dose of the drug, followed by 10-20 days of additional therapy, showed some serologic evidence of infection but no detectable viral RNA, Dr. Grob said, and the animals showed no evidence of latent infection. Dr. Grob added that his company is beginning to study nevirapine as a prophylactic treatment to prevent perinatal transmission of HIV.
The CDC expects to hold an additional meeting on postexposure treatment with its consultants later this year, and hopes to have draft guidelines available by year's end. Final recommendations may be ready next year.
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