Intravenous heroin users rely on a needle and syringe to inject the powerful opioid narcotic heroin directly into the bloodstream. In addition to the risks for drug addiction common to all people who take the drug, IV users have increased risks for serious or fatal bloodborne infections such as hepatitis C and HIV\/AIDS. In a study published in March 2014 in the International Journal of Drug Policy, researchers from four U.S. universities used a long-term project to identify the pathways that various individuals travel on their way to eventual involvement in IV heroin intake. Among other things, the researchers concluded that the typical pathways to this form of drug use are different for older and younger people. The Basics Just like any other legal or illegal opioid substance, heroin is addictive because its regular appearance in the brain produces long-term chemical changes that contribute to physical dependence and the onset of drug cravings and a highly dysfunctional, drug-oriented lifestyle. Since heroin is a particularly strong opioid, its use can lead to increasing problems even in someone accustomed to the intake of other opioid drugs or medications. In addition to IV injection, any given individual can consume the drug by snorting it or inhaling it after burning. All of these methods of use can lead to dependence and addiction. However, IV drug use is typically considered the gravest personal and public health risk, since such use can lead to the spread of both the human immunodeficiency virus (HIV) and the hepatitis C virus. Pathways to IV Heroin Use Public health officials are well aware that some of the people who eventually end up using heroin intravenously first participate in the abuse of some sort of opioid medication. All told, this form of illicit drug abuse ranks second in popularity only to marijuana use among U.S. adults and teenagers. Common examples of the medications used by prescription opioid abusers include oxycodone (found in products such as OxyContin and Percocet) and hydrocodone (found in products such as Vicodin and Lortab). However, not all people who become IV heroin users start with prescription opioid abuse or any other form of opioid use. Other drugs used previously by people who ultimately initiate IV heroin use include marijuana or some other form of cannabis, cocaine and methamphetamine. Which Pathways Are Most Common? In the study published in the International Journal of Drug Policy, researchers from the University of Pennsylvania, Columbia University, Harvard Medical School and the University of California, San Francisco used a long-term examination of heroin users in Philadelphia and San Francisco to help determine which drug-use pathways are most likely to end up in IV heroin intake. Data was gathered on the Philadelphia heroin users between 2007 and 2012; data was gathered on the San Francisco heroin users between 1994 and 2007, and again in 2012. All of the users involved in the project participated in extensive interview sessions; these interviews formed the core of a larger-scale observation of the behaviors of both heroin users and heroin dealers in the two cities. The researchers found that the pathways toward IV heroin intake typically differed for the young and old users in both Philadelphia and San Francisco. Most of the younger users started out by abusing oxycodone or some other opioid medication, went on to either smoke or snort heroin and eventually transitioned from these initial forms of heroin use into IV drug intake. While some of the older users in both cities also followed this pathway to IV heroin use, many \u00a0never abused an opioid medication. Instead, they abused marijuana (or hashish or hashish oil), cocaine or methamphetamine. Significance and Considerations The authors of the study published in the International Journal of Drug Policy note that most of the IV heroin users who started out by abusing an opioid medication attributed their transition to heroin intake to two main factors: the relatively easy availability of heroin as a target of opioid dependence and the low cost of heroin in relation to prescription opioids. In many cases, these individuals never really seriously considered the possibility that they could end up as intravenous drug users. The study\u2019s authors point out that many young heroin injectors were initially caught up in two historical trends: the steep rise in opioid prescriptions in the late 1990s and early 2000s and an increase in the availability of cheap, strong heroin that began in the early 1990s.