Truthfully? The people who get addicted to it have substance problems. The dr knows who is abusing it and who is not.
Well, tussionex is part hydrocodone which is a semi-synthetic opioid and part chlorpheniramine which is a type of antihistamine. So some people can be more sensitive to the hydrocodone (vicadin) part of the cough syrup. It is a fairly addictive drug and some people have genetics (an enzyme called cpy 2d6) that increases the duration the hydrocodone is elevated in their blood. This leads to exaggerated effects or feeling of euphora and other symptoms. It may be harder for these people to get off the cough syrup because they are sort of absorb it more so to speak. There are genetic tests to see if you have this enzyme. But they are not covered by insurance and can be expensive. So, any medication that has opioids and drugs that are addictive you should use with caution. A lot of people get easily addicted to codeine in cough syrup as well and this drug is similar.