Women need more frequent dosing of the antiviral medication Truvada — the only approved drug for preventing HIV infection — compared to men, according to a new study.
Researchers from University of North Carolina said that women need daily doses while men only need two doses a week because of how Truvada accumulates in various tissues in the body.
According to senior author and professor Angela Kashuba, the results show that a single dose doesn't fit all.
“In determining how best to use drugs to protect people from HIV, we need to understand where in their body they are at risk for being infected, along with the concentration of drug that is needed to protect that site from infection,” she explains.
The team used human cells in a test tube for measuring the amount of DNA material in the cells and how much of the drug was needed to prevent HIV infection in them. They then gave Truvada to 47 healthy females, sampling vaginal, cervical, and rectal tissues, and testing for drug levels and DNA material present in each person.
They found that twice as much Truvada is necessary to prevent infection in vaginal and cervical tissue than in rectal tissue, as fewer drug components were able to make it into those two types of tissue. The virus, too, uses more DNA material for reproducing in those two tissue types, requiring more of the medication to thwart infection.
And while the Food and Drug Administration recommends daily drug intake to both men and women since 2012, the former need not take Truvada more than two times a week.
The researchers said, however, that they would not recommend that people stop taking the drug daily, particularly without a doctor’s prior approval.
The findings were discussed in the Journal of Infectious Diseases.
Truvada is produced by Gilead and was approved in the United States as “pre-exposure prophylaxis” (PrEP) of HIV, a way to reduce infection risks.
The combination therapy of two HIV drugs – namely tenofovir and emtricitabine – performed well in clinical trials compared to a placebo, working to multiply inside CD4 cells or T-cells that are important in the fight against infections.
A gay man in Toronto, Canada, was recently diagnosed with HIV despite claiming to have religiously taken the pill for 24 months, marking the first report of the medication’s failure to work.
HIV specialist Dr. David Knox said that PrEP’s failure in this case could be due to a rare transmission of an HIV 1 strain resistant to both tenofovir and emtricitabine.
For experts, this may not necessarily be a show of ineffectiveness, but proof that PrEP may fail to work 100 percent, especially with sporadic or inconsistent intake.