Overdose toxicity refers to serious, often harmful, and sometimes fatal toxic reactions to an accidental overdose of a drug (because of a doctor's, pharmacist's, or patient's error) or to an intentional overdose (homicide or suicide).

A lower risk of overdose toxicity is often the reason doctors prefer one drug to another when both drugs are equally effective. For example, if a sedative, antianxiety drug, or sleep aid is needed, doctors usually prescribe benzodiazepines, such as diazepamSome Trade Names
DIASTAT VALIUM
and temazepamSome Trade Names
RESTORIL
, rather than barbiturates, such as pentobarbitalSome Trade Names
NEMBUTAL
. Benzodiazepines are not more effective than barbiturates, but they have a wider margin of safety and are much less likely to cause severe toxicity in case of an accidental or intentional overdose. Safety is also the reason that newer antidepressants, such as fluoxetineSome Trade Names
PROZAC
and paroxetineSome Trade Names
PAXIL
, have largely replaced older but equally effective antidepressants, such as imipramineSome Trade Names
TOFRANIL
and amitriptyline (see Mood Disorders: Drugs Used to Treat Depression).

Young children are at high risk of overdose toxicity. Brightly colored tablets and capsules, most of which are adult-dose formulations, can attract the attention of toddlers and young children. In the United States, federal regulations require that all prescription drugs taken by mouth be dispensed in childproof containers unless a person signs a waiver to the effect that such a container presents a handicap.

Most metropolitan areas in the United States have poison control centers that provide information about chemical and drug poisoning, and most telephone directories list the number of the local center. This number should be copied and placed near a telephone or programmed into an automatic-dialing telephone or cellular phone.

Last full review/revision October 2012 by Joan B. Tarloff, PhD