Background For successful implementation of PrEP as a HIV prevention strategy, participant’s adherence to the intervention is vital. Frequent interruption of study product, impacts its effectiveness negatively. We documented the frequency and causes of study drug interruptions among participants enrolled in the Partners PrEP Study, Thika-Kenya

Methods Between October 2008 and November 2010, we enrolled 496 HIV serodiscordant couples who were followed up to 36 months. We categorised time off study drug into two; protocol-defined, in which the parameters of withholding study drug was clearly outlined in the study protocol and participant-initiated interruption where the participant opted to stop taking study drug. Data on study drug interruptions were captured on monthly basis and documented on specific case report forms in pharmacy.

Results We reported 152 cases of study drug interruptions, these were contributed by 128 participants. Sixty four per cent of HIV-1 uninfected participants who recorded study drug interruption were male, median age for both gender was 31.8 (IQR 26.5, 37.4) years. Sixty five (43%) of reported drug interruptions were participant initiated, cited due to marital disharmony 34 (22%), fatigue and loss of interest 24 (16%), perceived side effects in 7 (5%). The median time off study product was 90 (IQR 28, 268) days. Age, gender and education were not associated with participant-initiated interruptions. Pregnancy and possible seroconversion were some of protocol defined reasons to stop study drug.

Conclusions Marital disharmony and loss of interest were two of the most common reasons for participant initiated interruption of study drug. Going forward, psychosocial support and continuous adherence counselling should be part of the package for successful implementation of PrEP for HIV prevention.