LD-50

LD50 or Lethal Dose, 50% is a measure used in toxicology to determine the dosage of a substance that is lethal to 50% of a test population. It is typically expressed in milligrams of substance per kilogram of body weight (mg/kg). The LD50 value is used to compare the toxicity of different substances and is a crucial factor in the development and testing of new drugs and chemicals.

Overview

The concept of LD50 was first introduced by J.W. Trevan in 1927. The LD50 test is performed on animals, such as rats, mice, and rabbits, and the results are used to predict the potential effects of the substance on humans. However, the accuracy of these predictions is often a subject of debate due to the differences in physiology and metabolism between humans and animals.

Calculation

The LD50 is calculated using statistical methods. A group of animals is exposed to varying doses of the substance, and the percentage of animals that die at each dose is recorded. The data is then plotted on a graph, and the dose that corresponds to 50% mortality is determined.

Criticism and Alternatives

The use of LD50 testing has been criticized due to ethical concerns about animal welfare. In response to these concerns, alternative methods have been developed, such as the Fixed Dose Procedure, the Up-and-Down Procedure, and the Acute Toxic Class Method. These methods aim to reduce the number of animals used and the severity of their suffering.

Applications

Despite its limitations, the LD50 value is widely used in various fields, including pharmacology, ecotoxicology, and occupational health and safety. It provides a simple and straightforward measure of toxicity that can be used to compare different substances and assess their potential risks.

File:LD50 graph.png

A typical graph showing the calculation of LD50

See Also

• Therapeutic index
• No-observed-adverse-effect level
• Median lethal dose
• Toxicity