Drug abuse is the use of illegal drugs or the use of prescription or over-the-counter medications in ways other than recommended or intended. It also includes intentional inhalation of household or industrial chemicals for their mind-altering effects. Tobacco use and problem drinking are sometimes included in the definition of drug abuse. Chemical abuse and substance abuse are terms sometimes used interchangeably with the term drug abuse, or they may be used to refer to a combination of drug abuse and tobacco use or problem drinking.