Health authorities in the United States are concerned some gay men are taking anti-HIV drug tenofovir in a bid to reduce the risk of transmission during unprotected sex.
Known colloquially as T, the medication is being sold at gay dance parties, and health officials say recreational use is growing, The Los Angeles Times reported.
Officials say there is no proof tenofovir reduces the risk of infection. They are also worried recreational use of the anti-HIV medication could increase general resistance to the drugs.
But prevention experts believe social use of tenofovir is still limited: about seven percent of HIV-negative gay men had taken an anti-AIDS drug before risky sex, according to a survey of four US cities released in July.