How do ED50 and LD50 measurements help scientists compare drug effects and toxicity?

Scientists use ED50 and LD50 measurements to evaluate the safety and efficacy of medications by calculating the therapeutic index, which is the ratio of LD50 to ED50.12

• ED50 (Median Effective Dose): This represents the dose at which 50 percent of a test population experiences the desired therapeutic effect. It is a primary tool for comparing the potency of different drugs that produce similar physiological results.12
• LD50 (Median Lethal Dose): This is the dose required to cause mortality in 50 percent of a test group of animals. It serves as a rough estimate of a substance's toxicity.12

By comparing these two values, researchers determine the margin of safety for a drug. A narrower margin indicates a higher likelihood of dangerous side effects, whereas a wider margin suggests a safer therapeutic profile. While these metrics are essential for drug development, they have significant limitations, as LD50 cannot be measured in humans and animal data may not accurately predict human responses.12