CDC recommendations for HIV chemoprophylaxis
The guidelines recently released by the federal Centers for Disease Control and Prevention mark a departure from its previously neutral stance on multiple-drug therapy for postexposure prophylaxis. For workers exposed to HIV, the CDC recommends:
1. Chemoprophylaxis should be recommended to exposed workers after occupational exposures associated with the highest risk for HIV transmission. For exposures with a lower, but non-negligible risk, postexposure prophylaxis should be offered, balancing the lower risk against the use of drugs having uncertain efficacy and toxicity. For exposures with negligible risk, postexposure prophylaxis is not justified. (See chart detailing the PHS postexposure chemoprophylaxis guidelines, p. 88.)
Exposed workers should be informed that: knowledge about the efficacy and toxicity of postexposure prophylaxis is limited; for agents other than zidovudine (AZT, Retrovir), data are limited regarding toxicity in people without HIV infection or who are pregnant; and any or all drugs for postexposure prophylaxis may be declined by the exposed worker.
2. At present, AZT should be considered for all postexposure prophylaxis regimens because it is the only agent for which data support the efficacy of postexposure prophylaxis in the clinical setting. Lamivudine (3TC) should usually be added to AZT for increased antiretroviral activity and activity against many AZT-resistant strains. A protease inhibitor (preferably indinavir [IDV] because of the characteristics summarized in the report) should be added for exposures with the highest risk for HIV transmission.
Adding a protease inhibitor also may be considered for lower risk exposures if AZT-resistant strains are likely, although it is uncertain whether the potential additional toxicity of a third drug is justified for lower risk exposures. For HIV strains resistant to both AZT and 3TC or resistant to a protease inhibitor, or if these drugs are contraindicated or poorly tolerated, the optimal postexposure prophylaxis regimen is uncertain; expert consultation is advised. (See note at end of recommendations.)
3. Postexposure prophylaxis should be initiated promptly, preferably within one to two hours postexposure. Although animal studies suggest that postexposure prophylaxis probably is not effective when started later than 24-36 hours postexposure,2,3 the interval after which there is no benefit from postexposure prophylaxis for humans is undefined. Initiating therapy after a longer interval (e.g., one to two weeks) may be considered for the highest risk exposures; even if infection is not prevented, early treatment of acute HIV infection may be beneficial.4
The optimal duration of postexposure prophylaxis is unknown; because four weeks of AZT appeared protective,5 postexposure prophylaxis probably should be administered for four weeks, if tolerated.
4. If the source patient or the patient's HIV status is unknown, initiating postexposure prophylaxis should be decided on a case-by-case basis, based on the exposure risk and likelihood of HIV infection in known or possible source patients. If additional information becomes available, decisions about postexposure prophylaxis can be modified.
5. Workers with occupational exposures to HIV should receive followup counseling and medical evaluation, including HIV antibody tests at baseline and periodically for at least six months postexposure (e.g., six weeks, 12 weeks, and six months), and should observe precautions to prevent possible secondary transmission.6 If postexposure prophylaxis is used, drug-toxicity monitoring should include a complete blood count and renal and hepatic chemical function tests at baseline and two weeks after starting postexposure prophylaxis. If subjective or objective toxicity is noted, dose reduction or drug substitution should be considered with expert consultation, and further diagnostic studies may be indicated. Health care workers who become infected with HIV should receive appropriate medical care.
6. Beginning July 15, health care providers in the United States are encouraged to enroll all workers who receive postexposure prophylaxis in an anonymous registry being developed by the Centers for Disease Control and Prevention, Glaxo Wellcome Inc., and Merck & Co. Inc., to assess toxicity [telephone (888) 737-4448]. Unusual or severe toxicity from antiretroviral drugs should be reported to the manufacturer and/or the Food and Drug Administration [telephone (800) 332-1088].
Updated information about HIV postexposure prophylaxis will be available beginning in early 1997 from the Internet at CDC's home page (http://www.cdc.gov); CDC's fax information service, telephone (404) 332-4565 (Hospital Infections Program directory); the National AIDS Clearinghouse, telephone (800) 458-5231; and the HIV/ AIDS Treatment Information Service, telephone (800) 448-0440.
[Note: An HIV strain is more likely to be resistant to a specific antiretroviral agent if it is derived from a patient who has been exposed to the agent for a prolonged period of time (e.g., six to 12 months or longer). In general, resistance develops more readily in persons with more advanced HIV infection (e.g., CD4+ T- lymphocyte count of less than 200 cells/mm3), reflecting the increasing rate of viral replication during later stages of the illness.]
References
1. Centers for Disease Control and Prevention. Update: Provisional Public Health Service recommendations for chemoprophylaxis after occupational exposure to HIV. MMWR 1996; 45:468-472.
2. Niu MT, Stein DS, Schnittman SM. Primary human immunodeficiency virus type 1 infection: Review of pathogenesis and early treatment interventions in humans and animal retrovirus infections. J Infect Dis 1993; 168: 1,490-1,501.
3. Gerberding JL. Management of occupational exposures to blood-borne viruses. N Engl J Med 1995; 332:444-451.
4. Kinloch-de Loes S, Hirschel BJ, Hoen B, et al. A controlled trial of zidovudine in primary human immunodeficiency virus infection. N Engl J Med 1995; 333:408-413.
5. Centers for Disease Control and Prevention. Case- control study of HIV seroconversion in health-care workers after percutaneous exposure to HIV-infected blood -- France, United Kingdom, and United States, January 1988-August 1994. MMWR 1995; 44:929-933.
6. Centers for Disease Control. Public Health Service statement on management of occupational exposure to human immunodeficiency virus, including considerations regarding zidovudine postexposure use. MMWR 1990; 39(No. RR-1):1-14. *
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