Ninety percent of Dr. Michael Sampson's HIV patients take Truvada as part of their treatment.
"It's very effective with very few side effects," said Sampson.
In the event of exposure, the drug can also be prescribed as a sort of "morning-after pill." Now the Food and Drug Administration may go a step further.
This week, the agency will consider approving the drug as a way to prevent HIV infection. In a three-year study, Truvada cut the risk in healthy gay and bisexual men 44 percent. Another study found it reduced infection 75 percent in heterosexual couples in which one partner was HIV-positive.
"It's very clear that for people who adhere to this medication there's a dramatic reduction in new HIV infections," said Phil Curtis, AIDS Project Los Angeles.
But the idea is not without controversy. Many in the AIDS community are concerned it will give people a false sense of security.
"A lot of people feel that if you give people a pill they will stop practicing what otherwise is known as safer-sex, using condoms, that sort of thing," said Curtis.
Like all anti-viral medications, compliance is key. Truvada must be taken once a day at the same time. If you don't and you acquire the infection, you could become resistant to treatment.
"You might be worse off than if you hadn't taken it to begin with," said Sampson. "We're stressing that safer sex and condom use should still be implemented."
Dr. Sampson says in some studies Truvada did not appear to protect women as well as men.
Also, long-term use may lead to kidney damage.
And then there's the cost: The drug runs about $11,000 a year. But FDA approval would mean insurance companies would cover it -- but it could take a while.
A panel of outside FDA advisors will meet Thursday to discuss which populations should take the drug, appropriate use and cost. A final decision on the drug is expected June 15.