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MICROBIOLOGY QUESTION: LD50: Amount of substance required to kill 50% of the test population Would you...

MICROBIOLOGY QUESTION:

LD50: Amount of substance required to kill 50% of the test population Would you want a drug being administered to have HIGH or LOW LD50 value? Is there a formula/ way to calculate this value?

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Expert Solution

Answer: LD means the lethal Dose and LD50 means the amount or quantity of drug or material needed to kill 50% of the population of the group which is under investigation. The LD50 is one of the most famous technique to measure the acute toxicity of a substance or drug. The LD50 technique was invented in 1927 by J.W. Trevan, who want to know the relative poisoning potency of drugs and medicines used in his experiments that time.

It is calculated that the lower the LD50 dose the more toxic is the drug or material. So that it is always advised that the for proper analysis of various results such as steps or mechanism of action analysis of a drug on the test animal the drugs having high LD50 values must be used because the drugs who have low LD50 value they have more toxicity and show very fast effect on test animal and the action mechanism in fast reaction is hard to understand. (this is only for the determination of mechanism of action of a drug). The LD50 is not valid for a human it is only determined on test animals.

Commonly the chemicals whose LD50 value is less than 300mg/kg, between 300-1000mg/kg and between 1000-5000mh/kg are considered as highly toxic, moderately toxic and slightly toxic respectively.

  1. The lethal Dose 50 (LD50) test procedure. On Animals

Species used for test: Monkeys, Rabbits, dogs, rats, mice, birds and fish

Method of dosing: (i) oral dosing (by a tube inserted down to the throat of animal) (ii) By injection (iii) Vapor inhaling (iv) By applying on skin.

Test duration: 14 days.

The common sign of poisoning (such as tears, diarrhea, bleeding from eyes and mouth, nose etc) is noted down.

On the bases of the effect of the drug on the animal, the LD50 of the drug or chemical is calculated.

2. The lethal Dose 50 (LD50) test procedure. On Bacterial system

The determination of LD 50 for the system is much easier than the animal system. The simplest procedure is given below:

Select a drug and make its different apply these concentrations of the on the bacterial systems and check the effect of the on bacterial population. Always run every reaction in triplicate and also run control with every experiment. The drug concentration which the 50% of the compared to the control is known as the LD50 of that drug for the microbial system.


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