Directly observed PrEP among people who inject drugs – useful for improving adherence?

The impact of adherence to preexposure prophylaxis on the risk of HIV infection among people who inject drugs.

Martin M, Vanichseni S, Suntharasamai P, Sangkum U, Mock PA, Leethochawalit M, Chiamwongpaet S, Curlin ME, Na-Pompet S, Warapronmongkholkul A, Kittimunkong S, Gvetadze RJ, McNicholl JM, Paxton LA, Choopanya K, Bangkok Tenofovir Study Group. AIDS. 2015 Apr 24;29(7):819-24. doi: 10.1097/QAD.0000000000000613.

Objective: To describe participant adherence to daily oral tenofovir in an HIV preexposure prophylaxis (PrEP) trial, examine factors associated with adherence, and assess the impact of adherence on the risk of HIV infection.

Design: The Bangkok Tenofovir Study was a randomized, double-blind, placebo-controlled trial conducted among people who inject drugs, 2005-2012.

Methods: Participants chose daily visits or monthly visits. Study nurses observed participants swallow study drug and both initialed a diary. We assessed adherence using the diary. We examined adherence by age group and sex and used logistic regression to evaluate demographics and risk behaviors as predictors of adherence and Cox regression to assess the impact of adherence on the risk of HIV infection.

Results: A total of 2413 people enrolled and contributed 9665 person-years of follow-up (mean 4.0 years, maximum 6.9 years). The risk of HIV infection decreased as adherence improved, from 48.9% overall to 83.5% for those with at least 97.5% adherence*. In multivariable analysis, men were less adherent than women (P = 0.006) and participants 20-29 years old (P < 0.001) and 30-39 years old (P = 0.01) were less adherent than older participants. Other factors associated with poor adherence included incarceration (P = 0.02) and injecting methamphetamine (P = 0.04).

Conclusion: In this HIV PrEP trial among people who inject drugs, improved adherence to daily tenofovir was associated with a lower risk of HIV infection. This is consistent with trials among MSM and HIV-discordant heterosexual couples and suggests that HIV PrEP can provide a high level of protection from HIV infection.

*The authors mean that effectiveness improved from 48.9% overall to 83.5% in those who were 97.5% adherent.

Abstract access  [1]

Editor’s notes: Randomised controlled trials have illustrated that daily oral tenofovir as pre-exposure prophylaxis (PrEP) can reduce HIV transmission. In this study, using data from the only PrEP trial to be completed among people who inject drugs, the investigators assessed the impact of directly-observed adherence to PrEP on the incidence of HIV infection in the Bangkok Tenofovir Study. Adherence was defined as the proportion of days recorded in the participants’ diaries that the participant took the study drug.  On average, participants took the study drug on 84% of days. Their findings of a strong association of increasing levels of adherence with reduced risk of HIV infection add to existing literature on the importance of adherence for PrEP effectiveness among gay men and other men who have sex with men and HIV-discordant couples. The novelty of this study was to directly observe adherence to PrEP.  Directly observed ART treatment has been used in prisons and drug treatment centres, and the potential of this method to improve adherence estimation is interesting.

Asia [5]
Thailand [6]
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