Analgesics, Opioid Article Cost-Benefit Analysis Decision Trees Drug Users Harm Reduction Hepatitis C Humans Needle Sharing Needle-Exchange Programs Opiate Substitution Treatment Opioid-Related Disorders Prevalence Quality-Adjusted Life Years Risk-Taking Substance Abuse, Intravenous United States adverse event antiviral therapy antivirus agent complication cost benefit analysis cost control cost effectiveness analysis decision tree drug use economics harm reduction health care cost health program