Minimum lethal dose

Minimum Lethal Dose (MLD) is a term used in Toxicology and Pharmacology to denote the lowest dose of a substance that can cause death in a living organism. It is a critical parameter in determining the Toxicity of substances and is used in risk assessments and regulatory decisions.

Definition

The Minimum Lethal Dose is defined as the smallest amount of a substance that, when administered in a single dose, is capable of causing death in a specified test species. It is usually expressed in terms of weight of the substance per weight of the test organism (e.g., milligrams of substance per kilogram of body weight).

Determination

The determination of the Minimum Lethal Dose is typically done through animal experiments. A group of animals is exposed to increasing doses of the substance, and the dose that causes death in 50% of the animals (the LD50) is often used as a proxy for the MLD. However, the actual MLD may be lower than the LD50, as some animals may die at lower doses.

Applications

The Minimum Lethal Dose is used in various fields, including:

• Toxicology: To assess the toxicity of new substances and to establish safety guidelines.
• Pharmacology: To determine the safety margin of drugs and to guide dose selection in clinical trials.
• Environmental science: To assess the risk posed by pollutants and other hazardous substances.
• Forensic science: To investigate cases of poisoning and overdose.

Limitations

While the Minimum Lethal Dose provides valuable information about the toxicity of a substance, it has several limitations:

• It does not provide information about the effects of repeated or chronic exposure to the substance.
• It does not take into account individual variations in susceptibility to the substance.
• It does not provide information about the specific effects of the substance on different organs or systems in the body.

See also

• Median lethal dose
• Therapeutic index
• Toxicity

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