As in "drug user". Outdated term describing a person who misuses drugs or alcohol, but not necessarily addicted. The term offers no distinction from chronic addictive behavior or use consistent with medical protocol.
A person addicted to heroin and a patient taking pain medicine are both "users". The term is stigmatizing because it labels a person by his/her behavior. It is also misleading because the term user has come to refer to one who is engaged in risky use of substances, but use alone (e.g. of alcohol or prescription medication) is not necessarily problematic.