Transition from first illegal drug use to first injection among people who inject drugs in Northern Mexico: A retrospective survival analysis

Introduction. There is little information in Mexico about the transition to injecting drugs among drug users in cities other than Tijuana. Objective. We compare characteristics of the onset of drug use and first injection among people who inject drugs (PWID) from Ciudad Juárez and Hermosillo, two cities of Northern Mexico and identify factors associated with faster rates of transition from first drug use to the first injection. Method. 841 PWID were interviewed in 2012 in Ciudad Juárez (n = 445) and Hermosillo (n = 396). Using lifetables, we describe timing at the onset of drug use and first injection. Cox regression analysis was used to determine factors associated with the transition hazard to first injection. Results. Median age at onset of drug use was 15.5 years old (standard deviation [SD] = 5.73). The median age at first injection was 21.30 (SD = 7.22). The median duration-time between first drug use and transition to injection was 4.8 years (SD = 5.6). Controlling for sociodemographics, factors that increase the hazard of transitioning to injection are age at onset of drug use (adjusted-hazard-rate [AHR] = 1.04, 95% confidence-interval CI [1.03, 1.05], p#abr#.01) having used cocaine, heroin, or methamphetamine at the onset of drug use (AHR = 1.14, 95% CI [1.03, 1.27], p = .01), and having received assistance at first injection (AHR = 1.25, 95% CI [1.17, 1.33], p#abr#.01). Discussion and conclusion. Results show the need to enhance harm reduction programs among non-injecting drug users so as to prevent the spread of injecting drugs in Mexico.