May 29, 2012

Antiretroviral Treatment for HIV Prevention

(Ivanhoe Newswire) -- A new study shows that pre-exposure preventative treatment for suspected HIV may be effective for those in high-risk groups.

"Although post-exposure prophylaxis has a long history of success, newer methods such as pre-exposure prophylaxis and earlier treatment in the course of infection ("treatment as prevention") are being implemented with some success," Dr. Isaac Bogoch, Harvard Medical School and the Division of Infectious Diseases, Massachusetts General Hospital, Boston, was quoted as saying.

There have been several recent large randomized controlled trials that helped physicians gain insight into pre-exposure prevention and early initiation of antiretroviral therapy. Researchers from Massachusetts General Hospital, Brigham and Women´s Hospital and Harvard Medical School, Boston, Massachusetts and Sunnybrook Health Sciences, Toronto conducted a review of literature from January 1990 to April 2012.

HIV is mainly transmitted through unprotected sex, contaminated needles, and from mother to baby, though the latter was not included in the review.

After it has been fully determined whether a person has been exposed to HIV, post-exposure treatment (prophylaxis) should begin as soon as possible or within 72 hours and be continued for 28 days. If the patient is in a low-risk situation but not completely without risk, both the physician and patient determine whether or not to begin prophylactic treatment. In current practice, a two-drug regimen of tenofovir with emtricitabine and a third drug in people with high risk exposure is recommended.

"Evidence for quickly starting prophylaxis and a four-week duration of therapy stem from macaque models of transmission, in which starting prophylaxis later and shorter durations of therapy resulted in higher rates of HIV seroconversion (development of antibodies against HIV," said the authors.

Pre-exposure prophylaxis has been shown to prevent HIV infection for high-risk populations such as men who have sex with men, intravenous drug users and women who live in an area with high prevalence of HIV. One trial involving 900 women living in an area with high HIV prevalence revealed a 39% reduction in HIV infection rates after application of a topical vaginal microbicide 12 hours before and after sex.

Pre-exposure prophylaxis interventions should be considered one part of a complete plan for preventing the spread of HIV infection that includes standard counseling on safer sexual practices and condom use, testing for and treating other sexually transmitted infections, and in some cases, male circumcision and needle exchange programs.

"Whereas pre-exposure prophylaxis may be reserved for people with the highest risk of exposure, the trend of treating HIV at higher CD4 T cell counts earlier in infection will likely show the most promise as a pharmacologic strategy for preventing transmission of the virus," said the authors.

Though pre-exposure prophylaxis is promising, there are questions that need to be determined such as which groups would benefit the most, the possibility of drug resistance, and others. There are already several trials underway designed to determine the effectiveness of early treatment.

SOURCE: Canadian Medical Association Journal, May 2012