title: The impact of adherence to preexposure prophylaxis on the risk of HIV infection among people who inject drugs.
abstract: 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.
  
  
  METHODS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: aThailand MOPH - US CDC Collaboration, Nonthaburi, Thailand bCenters for Disease Control and Prevention, Atlanta, USA cBangkok Tenofovir Study Group dBangkok Metropolitan Administration, Bangkok eThailand Ministry of Public Health, Nonthaburi, Thailand.
authors.forename: Michael
authors.initials: M
authors.lastname: Martin
authors.forename: Suphak
authors.initials: S
authors.lastname: Vanichseni
authors.forename: Pravan
authors.initials: P
authors.lastname: Suntharasamai
authors.forename: Udomsak
authors.initials: U
authors.lastname: Sangkum
authors.forename: Philip A
authors.initials: PA
authors.lastname: Mock
authors.forename: Manoj
authors.initials: M
authors.lastname: Leethochawalit
authors.forename: Sithisat
authors.initials: S
authors.lastname: Chiamwongpaet
authors.forename: Marcel E
authors.initials: ME
authors.lastname: Curlin
authors.forename: Supawadee
authors.initials: S
authors.lastname: Na-Pompet
authors.forename: Anchalee
authors.initials: A
authors.lastname: Warapronmongkholkul
authors.forename: Somyot
authors.initials: S
authors.lastname: Kittimunkong
authors.forename: Roman J
authors.initials: RJ
authors.lastname: Gvetadze
authors.forename: Janet M
authors.initials: JM
authors.lastname: McNicholl
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Paxton
authors.forename: Kachit
authors.initials: K
authors.lastname: Choopanya
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage; D004311:Double-Blind Method; D005260:Female; D015658:HIV Infections / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008499:Medical Records; D055118:Medication Adherence; D008875:Middle Aged; D065129:Pre-Exposure Prophylaxis / Q000379:methods*; D018570:Risk Assessment; D015819:Substance Abuse, Intravenous / Q000150:complications*; D000068698:Tenofovir / Q000008:administration & dosage; D055815:Young Adult
chemical_list: D019380:Anti-HIV Agents; D000068698:Tenofovir