A study has found that gay men who take a daily antiretroviral drug can cut their risk of getting infected with HIV by almost 45 per cent compared to those given a dummy pill.

The study published online in the New England Journal of Medicine found those who adhered most closely to the daily drug regimen had even higher prevention rates - their infection risk was up to 73 per cent lower.

The oral medication, sold under the brand name Truvada, combines two antiretroviral drugs and has been used for years to treat people already infected with HIV.

Lead researcher Dr. Robert Grant of the Gladstone Institute of Virology and Immunology in San Francisco says the study provides important evidence that the drug can reduce the risk of HIV infection among gay and bisexual men.

Grant says using the drug in combination with other prevention methods like consistent condom use could represent a major step forward in controlling the HIV epidemic.

The study of almost 2,500 men was conducted at 11 sites in Brazil, Ecuador, Peru, South Africa, Thailand and the United States.

"No single HIV prevention strategy is going to be effective for everyone," says Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases.

Fauci cautioned the findings only pertain to the effectiveness of the drug in men who have sex with men and cannot be extrapolated to other groups.