Free to Be Aware - HIV Prevention: A "Morning After" Pill?
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A "MORNING AFTER" RESCUE PILL? NO!
Desperately wanting to believe in its effectiveness, the public is prematurely embracing a potentially unsafe practice.
By Dan Bowers, MD
We urgently need new strategies to slow down the spread of HIV. With 5 million new cases a year worldwide and no vaccine in sight, pretreatment with an existing antiretroviral has seemed like a potential option. So far, a few studies have suggested that tenofovir (Viread) with or without emtricitabine (Emtriva) might be effective at knocking out HIV immediately after infection, but the data is far from conclusive. Unfortunately, society once again is moving ahead of science, since tenofovir is already being sold in dance clubs as a “morning after” pill. According to a study by the Centers for Disease Control and Prevention in four metropolitan areas, 7% of gay men reported using tenofovir before “risky behavior,” and 20% had heard of someone who had. But is this a good idea?
The use of a treatment medication to prevent infection is not new. Malaria prophylaxis, for example, is standard for travel to areas with ongoing malaria activity. We know that using antiretrovirals on women during labor and delivery can reduce the possibility of HIV transmission to a newborn by at least 50%. And the risk of transmission after a needle stick is decreased 80% with immediate initiation of antiretrovirals, which are then continued for four weeks.
As reported at last year’s Conference on Retroviruses and Opportunistic Infections, the use of emtricitabine plus tenofovir prevented transmission of simian immunodeficiency virus in monkeys. In that study six rhesus macaques were given injections of emtricitabine and tenofovir for nine days and were then exposed to SIV rectally every week for 14 weeks. Six other macaques received no prophylaxis. At the end of the study five of the “unprotected” monkeys were infected with SIV, but none of the treated monkeys picked up SIV. It is important to note that this is far better than a similar study in monkeys using tenofovir alone. As reported a year earlier at the 2005 retrovirus conference, four out of four monkeys on tenofovir became infected with SIV after weeks of exposure.
The latest data was presented in August at the International AIDS Conference. In this study 731 at-risk women in Cameroon and Ghana were given rigorous safe-sex counseling, including information on condom use, and then divided into two groups--one receiving tenofovir and one receiving a placebo. The women were seen monthly for testing and repeat counseling. After one year two of 363 on tenofovir seroconverted and six of 368 on a placebo seroconverted. While this was a 68% reduction in seroconversion, it was not statistically significant. However, more data is coming.
The CDC has three placebo-controlled trials under way. In Botswana the effectiveness of tenofovir plus emtricitabine is being studied in heterosexuals. In Thailand the effectiveness of tenofovir alone is being studied in injection-drug users. And in the United States a smaller study of 200 men who have sex with men in San Francisco and in Atlanta will look simply at the safety of using tenofovir versus a placebo and the behavioral effects of being on prophylaxis. (The National Institutes of Health has a study in Peru of 1,400 MSM to test tenofovir’s effectiveness.)
Data from these studies should be available in two to four years, but crucial questions need to be answered, especially since most experts do not expect medical prophylaxis to be 100% effective. For example, will there be a decline in concomitant safer-sex practices, like condom use, by patients when on prophylaxis? And if transmission does occur, will there be an increased amount of resistance to tenofovir or emtricitabine?
Meanwhile, back at the dance clubs there are men buying a false sense of security with one pill of tenofovir when we have evidence that tenofovir was not fully effective even when taken daily. Nor is there an effective level of the drug present after two days--about the time HIV reaches the lymph nodes and starts to replicate.
This is definitely not the time to be leaving the condoms behind.
Source: HIV Plus Mar / Apr 2007 issue http://www.hivplusmag.com/column.asp?id=1190&categoryid=4