Lethal dose

Lethal dose is a term used in toxicology to denote the amount of a substance that is sufficient to cause death in a living organism. The term is often used in the context of drug overdose, poisoning, and other forms of exposure to toxic substances. The lethal dose of a substance varies depending on the individual organism's size, age, sex, and overall health, as well as the route of exposure.

Definition

The lethal dose of a substance is typically expressed as LD50, which stands for "lethal dose, 50%". This is the dose required to kill half the members of a tested population after a specified test duration. LD50 figures are frequently used as a general indicator of a substance's acute toxicity.

Measurement

The LD50 measurement is usually expressed in milligrams of the substance per kilogram of body weight (mg/kg). The lower the LD50 value, the more toxic the substance is. For example, the LD50 of botulinum toxin (the most toxic substance known to man) is about 0.00001 mg/kg, while the LD50 of water is over 90,000 mg/kg.

Factors Influencing Lethal Dose

Several factors can influence the lethal dose of a substance. These include the route of exposure (ingestion, inhalation, skin contact), the duration of exposure, the rate of absorption, the distribution and metabolism of the substance in the body, and the individual's overall health and genetic makeup.

Examples

Some examples of substances and their approximate LD50 values (in rats, oral) include:

• Botulinum toxin: 0.00001 mg/kg
• Cyanide: 6.4 mg/kg
• Caffeine: 192 mg/kg
• Alcohol (ethanol): 7,060 mg/kg
• Water: >90,000 mg/kg

See Also

• Toxicity
• Poison
• Overdose
• Toxicology

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