The treatment, a combination of the anti-viral drugs used to slow the onset of Aids in HIV-infected people, was developed for health workers who accidentally prick themselves with syringes of contaminated blood.
Known as a post-exposure prophylaxis (PEP), it works by attacking the virus before it begins to replicate itself in human cells. Trials at the US Centres for Disease control have shown it cuts the risk of becoming HIV-positive by a needle prick by 80 per cent.
It has been available for 18 months to medical staff. Now news has filtered into the gay community, and some have received it at clinics following unsafe sex. But others have been refused the treatment, which can cost pounds 800 for a course of drugs usually lasting up to eight weeks, and must be started within 24 hours.
The gay community is split over PEP: some activists stress that a therapy available to health workers should not be denied to gay men, while others think it undermines the ethos of safe sex.
The treatment is outlined in Department of Health guidelines published next month: they mention in passing rape victims and men whose condoms break during sex. The campaigning Terrence Higgins Trust has expressed fears that gay men have been refused the treatment on cost grounds.
But Dr Brian Gazzard, clinical director at the Kohler HIV and Aids clinic in London, said he would never deny treatment because of cost. "The net cost to the NHS when balancing the drug against years of caring for someone with Aids is negligible."
"It isn't a simple decision," said Dr David Hawkins, of the Chelsea and Westminster hospital "These drugs are highly toxic ... They have unpleasant side effects. They don't actually guarantee complete protection."
He also said making the drugs widely available as a "morning after" treatment could have serious implications. "Anything that goes against safer sex behaviour would cause more infection in the gay population than this treatment would help."Reuse content