Study findings demonstrated that the gel, when applied to the vagina in previous trials, reduced HIV infection by 34% compared with placebo, which urged researchers to find out if it could work against anal transmission of HIV.
Researchers conducted biopsies of rectal tissues of 18 HIV-negative, sexually abstinent men and women after the initial dose, and followed it up with another biopsy round after a week of gel or placebo applications.
The HIV was then introduced into the biopsied cells in the lab.
It was found that the tissue cultures from patients who used the tenofovir gel daily for a week withstood HIV infection much better than those from patients who used placebo or the anti-HIV gel once.
Researchers also tested a single dose oral tablet and a single dose of rectal gel to find that those methods provided no protection against HIV.
Although the research suggested that the gel be a potential weapon in the fight against AIDS when applied to the rectum before anal intercourse, only 25% of the participants who tried it liked it. Some volunteers even experienced gastrointestinal side effects like diarrhea and cramps, the magazine reported.
The tenofovir daily pill is said to have a 20-fold higher active drug concentration compared to the gel.