Daily Tenofovir Pre-Exposure Prophylaxis Reduces HIV Transmission among People with Injection Drug Use in Drug Treatment

Pre-exposure prophylaxis with tenofovir/emtricitabine combination or tenofovir alone reduces the incidence of HIV infection from sexual transmission by about half, as long as adherence is adequate. Researchers conducted a randomized, placebo-controlled trial of daily pre-exposure prophylaxis with tenofovir among 2413 people in Bangkok, Thailand who injected drugs in the past year. Study sites were 17 drug treatment clinics that offered a package of HIV prevention interventions and directly observed therapy. Participants chose to receive medication via daily directly observed therapy or monthly visits and could switch monthly.

• At the beginning of the study, 33% of the sample abused methamphetamine, 22% abused heroin, 23% abused midazolam, and 22% were receiving methadone maintenance treatment.
• At the beginning of the study, the placebo group reported more sexual intercourse in the prior 12 weeks among men who had sex with men (6% versus 4%) and sex with a casual partner (40% versus 36%).
• Mean follow-up time was 4 years. Mean adherence was 84% of days. Participants received directly observed therapy 87% of the study days.
• Forty-five percent of participants reported at least one incidence of injection drug use during follow-up.
• There were 17 HIV seroconversions (incidence of 0.35 per 100 person-years) in the tenofovir group and 35 (0.68 per 100 person-years) in the placebo group, a 49% reduction in HIV incidence. HIV incidence did not differ until 36 months of follow-up.
• Nausea, vomiting (8% versus 5%), and increase in ALT (53% versus 49%) were more common in the tenofovir group.

Comments:

As in previous trials in sexual risk groups, in this trial among people who inject drugs pre-exposure prophylaxis cut HIV transmission in half. Adherence was key and likely bolstered by the study sites that were drug treatment centers that offered daily observed dosing and methadone maintenance. Analyses did not account for some imbalance at baseline in sexual risk that favored the tenofovir group.

Alexander Y. Walley, MD, Msc

Reference:

Choopanya K, Martin M, Suntharasamai P, et al. Antiretroviral prophylaxis for HIV infection in injecting drug users in Bangkok, Thailand (the Bangkok Tenofovir Study): a randomised, double-blind, placebo-controlled phase 3 trial. Lancet. 2013;381(9883):2083–2090.