Drug abuse is the use of a drug in a manner that is harmful or inappropriate, such as using it for a different purpose than intended or taking it in excessive amounts

. It can involve illegal drugs like heroin, cocaine, or methamphetamine, as well as the misuse of prescription or over-the-counter medicines

. Drug abuse often leads to problems including drug tolerance, dependence, addiction, and can negatively affect mental and physical health, relationships, work, and education

. More specifically, drug abuse refers to a maladaptive pattern of substance use that causes significant impairment or distress, such as failure to meet responsibilities, legal issues, or hazardous behavior like driving under the influence

. It is considered a form of substance-related disorder and can result in long-term changes to brain function, making it difficult to stop using despite harmful consequences

. In summary, drug abuse is the harmful or excessive use of substances, both legal and illegal, that leads to physical, psychological, social, and legal problems, often requiring treatment and support to overcome