MODEL RELEASED. Teenager injecting drugs. Teenage boy using a syringe to inject a drug into a vein in his arm. A tourniquet around his upper arm inflates the veins in his elbow and lower arm, making it easier to inject the drug. Illegal drugs injected in this way include liquid forms of heroin and cocaine. Drug users can become addicted to the drug they are using. They can also become infected by diseases transmitted through the reuse of needles.