title: Factors associated with the uptake of and adherence to HIV pre-exposure prophylaxis in people who have injected drugs: an observational, open-label extension of the Bangkok Tenofovir Study.
abstract: Results of the randomised, double-blind, placebo-controlled Bangkok Tenofovir Study (BTS) showed that taking tenofovir daily as pre-exposure prophylaxis (PrEP) can reduce the risk of HIV infection by 49% in people who inject drugs. In an extension to the trial, participants were offered 1 year of open-label tenofovir. We aimed to examine the demographic characteristics, drug use, and risk behaviours associated with participants' uptake of and adherence to PrEP.
  
  
  
  In this observational, open-label extension of the BTS (NCT00119106), non-pregnant, non-breastfeeding, HIV-negative BTS participants, all of whom were current or previous injecting drug users at the time of enrolment in the BTS, were offered daily oral tenofovir (300 mg) for 1 year at 17 Bangkok Metropolitan Administration drug-treatment clinics. Participant demographics, drug use, and risk behaviours were assessed at baseline and every 3 months using an audio computer-assisted self-interview. HIV testing was done monthly and serum creatinine was assessed every 3 months. We used logistic regression to examine factors associated with the decision to take daily tenofovir as PrEP, the decision to return for at least one PrEP follow-up visit, and greater than 90% adherence to PrEP.
  
  
  
  Between Aug 1, 2013, and Aug 31, 2014, 1348 (58%) of the 2306 surviving BTS participants returned to the clinics, 33 of whom were excluded because they had HIV (n=27) or grade 2-4 creatinine results (n=6). 798 (61%) of the 1315 eligible participants chose to start open-label PrEP and were followed up for a median of 335 days (IQR 0-364). 339 (42%) participants completed 12 months of follow-up; 220 (28%) did not return for any follow-up visits. Participants who were 30 years or older (odds ratio [OR] 1·8, 95% CI 1·4-2·2; p<0·0001), injected heroin (OR 1·5, 1·1-2·1; p=0·007), or had been in prison (OR 1·7, 1·3-2·1; p<0·0001) during the randomised trial were more likely to choose PrEP than were those without these characteristics. Participants who reported injecting heroin or being in prison during the 3 months before open-label enrolment were more likely to return for at least one open-label follow-up visit than those who did not report injecting heroin (OR 3·0, 95 % CI 1·3-7·3; p=0·01) or being in prison (OR 2·3, 1·4-3·7; p=0·0007). Participants who injected midazolam or were in prison during open-label follow-up were more likely to be greater than 90% adherent than were those who did not inject midazolam (OR 2·2, 95% CI 1·2-4·3; p=0·02) or were not in prison (OR 4·7, 3·1-7·2; p<0·0001). One participant tested positive for HIV, yielding an HIV incidence of 2·1 (95% CI 0·05-11·7) per 1000 person-years. No serious adverse events related to tenofovir use were reported.
  
  
  
  More than 60% of returning, eligible BTS participants started PrEP, which indicates that a substantial proportion of PWID who are knowledgeable about PrEP might be interested in taking it. Participants who had injected heroin or been in prison were more likely to choose to take PrEP, suggesting that participants based their decision to take PrEP, at least in part, on their perceived risk of incident HIV infection.
  
  
  
  US Centers for Disease Control and Prevention and the Bangkok Metropolitan Administration.
authors.affiliation: Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand; Centers for Disease Control and Prevention, Atlanta, GA, USA. Electronic address: znd9@cdc.gov.
authors.forename: Michael
authors.initials: M
authors.lastname: Martin
authors.affiliation: Bangkok Tenofovir Study Group, Taksin Hospital, Bangkok, Thailand.
authors.forename: Suphak
authors.initials: S
authors.lastname: Vanichseni
authors.affiliation: Bangkok Tenofovir Study Group, Taksin Hospital, Bangkok, Thailand.
authors.forename: Pravan
authors.initials: P
authors.lastname: Suntharasamai
authors.affiliation: Bangkok Tenofovir Study Group, Taksin Hospital, Bangkok, Thailand.
authors.forename: Udomsak
authors.initials: U
authors.lastname: Sangkum
authors.affiliation: Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Mock
authors.affiliation: Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand.
authors.forename: Benjamaporn
authors.initials: B
authors.lastname: Chaipung
authors.affiliation: Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand.
authors.forename: Dararat
authors.initials: D
authors.lastname: Worrajittanon
authors.affiliation: Bangkok Metropolitan Administration, Bangkok, Thailand.
authors.forename: Manoj
authors.initials: M
authors.lastname: Leethochawalit
authors.affiliation: Bangkok Metropolitan Administration, Bangkok, Thailand.
authors.forename: Sithisat
authors.initials: S
authors.lastname: Chiamwongpaet
authors.affiliation: Department of Disease Control, Thailand Ministry of Public Health, Nonthaburi, Thailand.
authors.forename: Somyot
authors.initials: S
authors.lastname: Kittimunkong
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Roman J
authors.initials: RJ
authors.lastname: Gvetadze
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Janet M
authors.initials: JM
authors.lastname: McNicholl
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Paxton
authors.affiliation: Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand; Centers for Disease Control and Prevention, Atlanta, GA, USA; Division of Infectious Diseases, Oregon Health and Sciences University, Portland, OR, USA.
authors.forename: Marcel E
authors.initials: ME
authors.lastname: Curlin
authors.affiliation: Thailand Ministry of Public Health-US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand; Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Holtz
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Taraz
authors.initials: T
authors.lastname: Samandari
authors.affiliation: Bangkok Tenofovir Study Group, Taksin Hospital, Bangkok, Thailand.
authors.forename: Kachit
authors.initials: K
authors.lastname: Choopanya
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage; D004311:Double-Blind Method; D055030:Drug Users; D015658:HIV Infections / Q000453:epidemiology / Q000517:prevention & control / Q000821:virology; D015497:HIV-1 / Q000187:drug effects; D015994:Incidence; D055118:Medication Adherence; D065129:Pre-Exposure Prophylaxis; D012309:Risk-Taking; D015819:Substance Abuse, Intravenous / Q000150:complications; D000068698:Tenofovir / Q000008:administration & dosage; D013785:Thailand / Q000453:epidemiology; D013997:Time Factors; D017322:Clinical Trials, Phase II as Topic; D017326:Clinical Trials, Phase III as Topic; D016032:Randomized Controlled Trials as Topic
chemical_list: D019380:Anti-HIV Agents; D000068698:Tenofovir