Background:  ART concentrations may differ in the genital tract (GT) and blood plasma (BP). Drugs that poorly penetrate the genital tract may lead to increases in genital tract viral load and possible development of resistance. We assessed genital tract ART concentrations among women on chronic HAART.

Methods:  We enrolled in an ongoing study, 34 women on HAART whose plasma viral load ≤80 copies/mL for at least 6 months. Paired direct genital tract aspirate and blood samples were collected in the morning prior to ART intake and 3 hours after. Genital tract and blood plasma drug concentrations were analyzed by validated liquid chromatography/ultraviolet detection or mass spectroscopy methods. Drug concentrations were log-transformed prior to analysis; ratios and 95% confidence intervals were estimated by back-transforming the difference in means and confidence interval of the paired blood and genital tract drug concentrations at each time period and of the genital tract concentrations following and prior to ART intake.

Results:  The extracellular concentrations of zidovudine (ZDV), lamivudine (3TC), emtricitabine (FTC), tenofovir (TDF) in the genital tract were higher than blood plasma. All drugs showed significant increase in blood plasma at 3 hours. The non-nucleoside reverse transcriptase inhibitors (NNRTI) and protease inhibitors (PI) showed poor concentrations in the genital tract. Only 1 woman had detectable genital tract and plasma viral load (EFV, 3TC, didanosine [ddI]).

Conclusions:  Several NRTI (ZDV, 3TC, FTC, and TDF) achieve genital tract exposures greater than in blood plasma. They may be effective in suppressing genital tract viral levels and also have utility in  preventing sexual as well as mother-to-child transmission of HIV.