title: Enrollment characteristics and risk behaviors of injection drug users participating in the Bangkok Tenofovir Study, Thailand.
abstract: BACKGROUND
  The Bangkok Tenofovir Study was launched in 2005 to determine if pre-exposure prophylaxis with tenofovir will reduce the risk of HIV infection among injecting drug users (IDUs). We describe recruitment, screening, enrollment, and baseline characteristics of study participants and contrast risk behavior of Tenofovir Study participants with participants in the 1999-2003 AIDSVAX B/E Vaccine Trial.
  
  
  METHODS
  The Bangkok Tenofovir Study is an ongoing, phase-3, randomized, double-blind, placebo-controlled, HIV pre-exposure prophylaxis trial of daily oral tenofovir. The Tenofovir Study and the Vaccine Trial were conducted among IDUs at 17 drug-treatment clinics in Bangkok. Tenofovir Study sample size was based on HIV incidence in the Vaccine Trial. Standardized questionnaires were used to collect demographic, risk behavior, and incarceration data. The Tenofovir Study is registered with ClinicalTrials.gov, number--NCT00119106.
  
  
  RESULTS
  From June 2005 through July 2010, 4094 IDUs were screened and 2413 enrolled in the Bangkok Tenofovir Study. The median age of enrolled participants was 31 years (range, 20-59), 80% were male, and 63% reported they injected drugs during the 3 months before enrollment. Among those who injected, 53% injected methamphetamine, 37% midazolam, and 35% heroin. Tenofovir Study participants were less likely to inject drugs, inject daily, or share needles (all, p<0.001) than Vaccine Trial participants.
  
  
  CONCLUSIONS
  The Bangkok Tenofovir Study has been successfully launched and is fully enrolled. Study participants are significantly less likely to report injecting drugs and sharing needles than participants in the 1999-2003 AIDSVAX B/E Vaccine Trial suggesting HIV incidence will be lower than expected. In response, the Bangkok Tenofovir Study enrollment was increased from 1600 to 2400 and the study design was changed from a defined 1-year follow-up period to an endpoint-driven design. Trial results demonstrating whether or not daily oral tenofovir reduces the risk of HIV infection among IDUs are expected in 2012.
authors.affiliation: Thailand Ministry of Public Health - US Centers for Disease Control and Prevention Collaboration, 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: Rutt
authors.initials: R
authors.lastname: Chuachoowong
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: Somyot
authors.initials: S
authors.lastname: Kittimunkong
authors.forename: Frits
authors.initials: F
authors.lastname: van Griensven
authors.forename: Janet M
authors.initials: JM
authors.lastname: McNicholl
authors.forename: Lynn
authors.initials: L
authors.lastname: Paxton
authors.forename: Kachit
authors.initials: K
authors.lastname: Choopanya
mesh_terms: D016915:AIDS Vaccines / Q000627:therapeutic use*; D000225:Adenine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000284:Administration, Oral; D000328:Adult; D003140:Communicable Disease Control; D004311:Double-Blind Method; D005260:Female; D015658:HIV Infections / Q000150:complications / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D063065:Organophosphonates / Q000627:therapeutic use*; D010919:Placebos; D012306:Risk; D012309:Risk-Taking; D015819:Substance Abuse, Intravenous / Q000150:complications*; D000068698:Tenofovir; D013785:Thailand
chemical_list: D016915:AIDS Vaccines; C112734:AIDSVAX; D063065:Organophosphonates; D010919:Placebos; D000068698:Tenofovir; D000225:Adenine