Preventive ART Therapy Dosing May Vary By Gender

Women may need more frequent ART doses to prevent HIV transmission than men, a mathematical model suggests.

Women must take antiretroviral Truvada more often than men to prevent HIV transmission from sex, the results of a new mathematical model suggest.

According to pharmacy researchers from the University of North Carolina, women must take the medication daily in order to prevent HIV transmission via vaginal sex, whereas men can be protected from HIV transmission via anal sex by taking the medication twice a week.

The model explains the inefficacy of HIV pre-exposure prophylaxis seen in 2 large clinical trials. Those trials, VOICE and FEM-PrEP, tested Truvada and tenofovir for HIV prevention, and counseled patients to take 1 of the medications daily. Despite the recommendation, participants only took the antiretroviral 29% of the time in VOICE and 36% of the time in FEM-PrEP.

Researchers first determined the intracellular ratios of tenofovir and emtricitabine, the drugs in Truvada, to DNA molecules needed to prevent HIV replication. They then used data from early clinical trials in women to predict the ratios in vaginal, cervical, and rectal tissues given standard medication doses, and calculated the percentage of the study population that achieve the ratio preventing HIV replication at various dosing frequencies.

The model predicts 2 weekly doses of Truvada or a daily standard dose of tenofovir will achieve the ratio needed to prevent HIV replication in rectal tissue. Meanwhile, a standard daily Truvada dose achieves the target ratio in vaginal tissue in more than 75% of participants, and in cervical tissue in half of participants.

The standard daily dose of tenofovir achieves the target ratio in cervical and vaginal tissues in less than have of participants, the model suggests. According to researchers, achieving the target ration is easier in rectal tissue because the concentration of DNA molecules is lower, and of tenofocir is higher in rectal tissue than in vaginal or cervical tissue.