Liu said out of 1,800 men questioned, only 16 percent had heard of using antiretroviral drugs to prevent HIV transmission, and 1 percent admitted to ever trying them on their own.
A similar study of more than 227 men in Boston, from the Fenway Community Health Center, found one person who had tried using PreP in place of a condom.
While those numbers seem low, doctors, HIV activists and public health officials believe that the number of people using PreP as an ill-advised condom replacement would grow with an FDA approval of a PreP regimen.
"The problem with it is the idea of a disinhibitor," said Sean Strub, founder of POZ magazine (www.poz.com/).
"I think of it more in terms of Gardasil and also, even birth control," said Strub. "Virtually every woman who becomes pregnant and did not want to be knows how to avoid it. It's applying that knowledge at the moment of sexual interaction that gets complicated."
Just as with many drugs or treatments that protect against risk, activists and doctors must evaluate whether people will gamble with semi-effective protection and further spread more disease than if they'd never had access to the protection in the first place.
But Strub, who had heard about the possibility of PreP years ago, said the public could also encourage safe-sex advances.
"Quite frankly, it surprises me that people aren't doing this," he said. "Most of the major advances of HIV prevention have not come from the CDC or the doctors or the government. It comes from the community."
Strub said this year marks the 26th anniversary of a pamphlet "How to Have Safe Sex in an Epidemic," first calling for the use of condoms to protect against HIV, written by community activists. Since that time, controversial additional behaviors, such as serosorting (restricting partners to your HIV status) have evolved.
But, unlike the condom, a pre-exposure pill comes with many more nagging medical details.
"The important thing to realize is that it's not just an evening-before pill that people pop," said Liu, who is currently directing the Prepare trial of a combination drug called Truvada among 3,000 men in the United States, South America, Asia and Africa.
Liu said the current testing is for a daily pill. Doctors still are checking for side effects of liver or kidney damage. Moreover, people in the study need routine HIV testing and follow-up care.
"These are men who are at risk for HIV, and since we don't know yet whether this approach works, we want to keep them on the best prevention," he said.
Costs of the drug may also be an issue.
"The medications that are involved are costly, and depending on whose paying for them, different payers or insurance, it could be a problem," said Dana Van Goder, executive director of Project Inform, a community-based HIV/AIDS awareness program in San Francisco.
Van Goder estimates the drugs, as they are sold now, would cost $500 to $900 a month. That would presumably go down if the drugs were made more widely available.
Whatever the future of the pill may be, Dennis believes he helped somebody in the trial.
"Having the knowledge that there's such a drug out there was real encouraging," said Dennis. "It's a very small part, but if I could do something to help this along I felt like I should."