Very high levels of adherence have been achieved in one of the ongoing randomised controlled trials of oral pre-exposure prophylaxis (PrEP), according to a poster presentation at last month’s Conference on Retroviruses (CROI).
According to investigators in the Partners PrEP study, adherence levels of 99% were achieved by participants during an average four-month period during the two-year study.
Partners PrEP is a study amongst 4700 heterosexual couples of differing (serodiscordant) HIV status at nine sites in Kenya and Uganda. The HIV-negative member of each couple will be randomised into three groups to take a daily pill containing tenofovir, or tenofovir plus FTC, or a placebo. All pills will look identical. At the end of the study HIV incidence rates in the three trial arms will be compared. Results are expected by early 2013.
Achieving high adherence to the study medication in trials of new biomedical prevention methods such as microbicides and oral PrEP has been a challenge in studies so far, even those achieving a successful result.
Conventional methods of adherence monitoring such as self-report have proved to be unreliable, as drug level monitoring (in the iPrEx PrEP trial) and the use of microbicide applicators sensitive to vaginal mucus (in the Carraguard microbicide trial) have shown that participants’ actual use of trial interventions is considerably lower than their reported use.
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