Several clinical trials have demonstrated the safety and effectiveness of oral tenofovir disoproxil fumarate (TDF), with or without emtricitabine (FTC), as pre-exposure prophylaxis (PrEP) for reducing the risk of HIV acquisition. Adherence to the study product was insufficient to demonstrate the effectiveness of FTC/TDF in 2 PrEP clinical trials conducted among women (FEM-PrEP and the Vaginal and Oral Interventions to Control the Epidemic study), but further analyses of adherence in these studies may inform PrEP demonstration projects and future HIV prevention clinical trials.
We randomly selected a subcohort of 150 participants randomized to FTC/TDF in 3 FEM-PrEP sites (Bondo, Kenya; Bloemfontein, South Africa; and Pretoria, South Africa) to examine adherence levels over time and to assess factors associated with adherence, based on plasma tenofovir and intracellular tenofovir diphosphate drug concentrations in specimens collected at 4-week visit intervals.
We observed drug concentrations consistent with good adherence in 28.5% of all visit intervals when drug was available to use, but only 12% of participants achieved good adherence throughout their study participation. In multivariate analysis, the Bloemfontein site [odds ratio (OR): 2.43; 95% confidence interval (CI): 1.32 to 4.48] and liking the pill color (OR: 2.93; 95% CI: 1.18 to 7.27) were positively associated with good adherence, whereas using oral contraceptive pills at enrollment was negatively associated with good adherence (OR: 0.37; 95% CI: 0.18 to 0.74).
Most participants did not regularly adhere to the study product throughout their trial participation, although a small minority did. Few factors associated with good adherence to the study product were identified in FEM-PrEP.
Departments of *Social and Behavioral Health Sciences,
†Clinical Sciences, and
‡Quantitative Sciences, FHI 360, Durham, NC;
§Setshaba Research Centre, Soshanguve, South Africa;
‖Impact Research and Development Organization, Kisumu, Kenya;
¶Josha Research, Bloemfontein, South Africa;
#Kilimanjaro Christian Medical Center, Moshi, Tanzania; and
**Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC (Van Damme is now with the Bill & Melinda Gates Foundation, Seattle, WA).
Correspondence to: Amy L. Corneli, MPH, PhD, Social and Behavioral Health Sciences, 359 Blackwell Street, Suite 200, Durham, NC 27701 (e-mail: email@example.com).
FEM-PrEP was conducted under 2 grants funded by the United States Agency for International Development (USAID): the Contraceptive and Reproductive Health Technologies and Research Utilization Program and the Preventive Technologies (Agreement No. GHO-A-00-09-00016-00). Early support was also provided by the Bill & Melinda Gates Foundation. Gilead Sciences, Inc. donated FTC/TDF and placebo. The drug concentration analyses were performed using equipment provided by the University of North Carolina at Chapel Hill Center for AIDS Research (CFAR), an NIH funded program P30 AI50410.
The authors have no conflicts of interest to disclose.
For a complete listing of participating members of FEM-PrEP Study Group, see Appendix 1.
This is an open access article distributed under the terms of the Creative Commons Attribution-Noncommercial No Derivative 3.0 License, which permits downloading and sharing the work provided it is properly cited. The work cannot be changed in any way or used commercially.
Received December 03, 2013
Accepted February 25, 2014