LD50
Definition
Median lethal dose; the dose of a substance that kills 50% of a test population, expressed as mg/kg body weight. The classical comparator of acute toxicity across compounds and species.
- Meaning
- Median lethal dose
- Population effect
- Kills 50% of test subjects
- Units
- mg/kg body weight
- Use
- Comparative measure of acute toxicity
Common questions
Does LD50 predict the outcome for a specific individual?+
Not directly. It is a statistical value derived from a population, typically animal studies, and individual susceptibility varies with body weight, age, health, and route of exposure, so a case involving a real person needs those factors considered separately.
How is LD50 used in forensic toxicology casework?+
It gives a benchmark against which a measured or estimated dose can be compared to judge whether a lethal or near-lethal amount was likely ingested, supporting an opinion on cause of death alongside postmortem tissue concentrations and case circumstances.
Related terms
- First-Pass Metabolism
- Hepatic and gut wall biotransformation of orally absorbed drug before it reaches systemic circulation. Bypassed by IV, intramuscular, inhalation and most dermal...
- Idiosyncrasy
- A qualitatively abnormal response to a normal dose, traceable to genetic polymorphism in metabolising enzymes, transporters or receptor targets. Not the same...
- Pharmacogenomics
- Study of how inherited variation in drug-metabolising genes (CYP2D6, CYP2C19, NAT2, G6PD) changes drug response. The Indian Genome Variation Consortium and ICMR...
- Tolerance
- Reduced response to a given dose after repeated exposure. Pharmacokinetic tolerance is enzyme induction or transporter upregulation; pharmacodynamic tolerance is receptor downregulation...
- Volume of Distribution (Vd)
- The apparent volume in which a drug is distributed in the body, calculated as dose divided by plasma concentration at time zero....