Drug toxicity refers to the level of damage that a compound can cause to an organism. The toxic effects of a drug are dose-dependent and can affect an entire system as in the CNS or a specific organ such as the liver. Drug toxicity usually occurs at doses that exceed the therapeutic efficacy of a drug; however, toxic and therapeutic effects can occur simultaneously. It can be assessed at the behavioral or physiological level. Behaviorally, drug toxicity can be exhibited in a variety of ways, for example, decreases in locomotor activity, loss of motor coordination, cognitive impairment.