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HIV & AIDS Health Center

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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...

All couples were given intensive counseling about safer sex practices, contraceptives, condoms, and monitoring and treatment for STDs.

The couples were evenly divided into three groups: one took a daily placebo pill, the second got a daily dose of the drug tenofovir, and a third was assigned to a daily combination pill with the drugs tenofovir and emtricitabine, which is sold under the brand name Truvada.

After 36 months, 78 new HIV infections had occurred in the study. There were 18 in those taking tenofovir alone, 13 in those assigned to the combination pill, and 47 among those who were taking a placebo.

Those who were taking tenofovir alone had an average of 62% fewer HIV infections, while those who received the combination pill had 73% fewer infections than those on the placebo. The differences between the two groups were not statistically significant, meaning one regimen was not better than the other.

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.

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