Martin, M., Vanichseni S., Suntharasamai P., et al. The Lancet HIV (February 2017), 4: e59–66, doi:10.1016/S2352-3018(16)30207-7.
Results of the Bangkok Tenofovir Study (BTS), a randomized, double-blind, placebo-controlled, HIV pre-exposure prophylaxis (PrEP) study in Thailand, showed that taking tenofovir daily as PrEP can reduce the risk of HIV infection by 49 percent among people who inject drugs (PWID). Between 2013–2014, an extension to the trial offered non-pregnant, non-breastfeeding, HIV-negative BTS participants (all current or previous PWID at the time of enrollment in BTS) daily oral tenofovir via 17 Bangkok Metropolitan Administration drug treatment clinics. Afterward, researchers followed up with participants to examine demographic characteristics, drug use, and risk behaviors. Of the BTS participants, 798 chose to start taking daily PrEP (35% of all surviving participants and 61% of those who returned and were eligible). Although overall adherence was low, 25 percent of participants who returned for at least one open-label follow-up visit were more than 90 percent adherent; and 59 percent returned for the 12-month visit. Participants who injected heroin or had been in prison were more likely to choose to take PrEP, suggesting that participants partly based their decision on their perceived risk of infection. The authors note that findings suggest that PWID can assess their risk of HIV infection and decide appropriately whether or not to take PrEP.