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1. Median Lethal Dose(LD50)
NAME: Muhammad Haider Ali
ROLL NO: 43
TOPIC:

2. Definition:
LD stands for "Lethal Dose". LD50 is the amount of a dose, given all at once,
which causes the death of 50% (one half) of a group of test animals. The LD50 is
one way to measure the acute toxicity of a material.
Toxicologists can use many kinds of animals but most often testing is done with
rats.
The LD50 can be found for any route of entry or administration but dermal
(applied to the skin) and oral (given by mouth) administration methods are the
most common.
Initially introduced by J.W. Trevan in 1927.

3. Importance:
It is an initial step in the assessment and evaluation of the toxicity of a
substance.
To determine the therapeutic index (TI) i.e. ratio between the median lethal
dose and the effective dose in the same strain and species (LD50/ED50). The
greater the index, safer is the compound.
The test is used to measure acute systemic toxicity.
The smaller the LD50 value, the more toxic is the drug and larger the LD50
value, lower is the toxicity of that particular drug.

4. Limitations of LD50:
Only for acute toxicity.
Cannot provide information on chronic, or long term, toxicity;
Example: lead will build in the body over time and result in poisoning when
concentration becomes too high.

5. Scales Used:
Two most common scales used are the ;
Hodge and Sterner Scale
Gosselin, Smith and Hodge Scale

8. Methods of LD50:
Two most common methods used;
Arithmetical method:
Graphical Method:

9. Factors Affecting LD50:
Species, age, sex, bodyweight, general health condition, diet, nutritional status
and number of animals used in the test.
Route of administration (oral route differ from parenteral route)
Environmental Conditions (lab conditions) i.e. intra and inter laboratory
conditions.
Experimental procedures and Dosage Formulations.

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