PrEP For Injection Drug Users: Bangkok Tenofovir Study

More than half of the 2,306 surviving participants in the original study returned for the extension trial and over 60% of those returning began PrEP. Participants with a higher risk of HIV infection - a recent stay in prison or heroin injection - were more likely to return for a follow-up than the general population. Former prisoners were also more likely to take their pill daily at least 90% of the time, as were those who inject the anti-anxiety medication midazolam, compared to the rest of the study population.

The investigators remark that the availability of tenofovir disproxil fumarate in penitentiary polyclinics improved adherence among that group. They also hypothesize that overall lower adherence rates in the extension trial compared to the original study may be due to lower rates of reported needle sharing in the open-label trial than at the beginning of the original trial. Participants who do not share needles may not take PrEP daily because of their lower risk of seroconversion.