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Antiretroviral Drugs May Prevent HIV Infection

Studies Show Once-Daily Pill May Cut HIV Infection Risk by up to 73%

Testing Medication to Prevent HIV continued...

Researchers reported having very high levels of medication adherence in their study, saying that more than 97% of dispensed pills were taken. That was determined by the number of pills that were returned to study investigators at monthly check-in visits. Researchers have also taken blood tests to confirm blood levels of the study medications, but those results have not yet been analyzed, they said.

An independent panel of experts found the early results of the study so compelling that they ordered the placebo portion of the study stopped early so that those participants could have access to the study medications.

The study was funded by the Bill & Melinda Gates Foundation.

The second study, called the TDF2 trial, directed by the CDC, tracked about 1,200 young, sexually active men and women in Botswana and Uganda. None had been previously infected with HIV.

They were randomly assigned to take either a daily placebo pill or Truvada.

After roughly three years, there were nine new HIV infections among adults taking Truvada compared to 24 in those assigned to the placebo, representing a 63% reduction in infection risk.

Among those who were thought to have taken the study drugs as directed, protection was even greater, rising to 78%.

Researchers said adherence to the medication regimens was high. About 84% of people in the study took their pills as directed, as determined by pill counts at regular check-in visits.

Additionally, there were no safety concerns identified in either study.

Both studies are due to be presented next week at the International AIDS Society Meeting in Rome.

Applying the Study Findings to the U.S.

Independent experts said that while the study results appear to be very promising, it was unclear how they might translate to people in the U.S.

Bruce Hirsch, MD, attending physician of infectious disease at North Shore LIJ Health System in New York said most of his HIV-positive patients in committed relationships were already taking substantial precautions to avoid passing the virus on to their partners.

Those precautions include using condoms and taking antiretroviral medications, like the ones used in these studies.

When those drugs are taken by HIV-infected people, they can reduce the risk of transmission to uninfected partners by 97%, Hirsch says.

"I think of a person who would use this medication as a person who is not in a committed relationship, who is maybe an unusual combination of being responsible and not so responsible, who wants to make unsafe sex a little safer," Hirsch says.

"It's a little bit hard for me to conceive of a person so thoughtful and so health conscious that he or she would take this step but not use barrier precautions," Hirsch says.

It's also unclear whether insurance would pick up the tab when the drugs are used in healthy people. By some estimates, Truvada costs between $12,000 and $14,000 a year in the U.S.

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