drug reaction IC50, EC50, GI50, LD50

There are four ways to quantify drug responses.
1. IC50: Half maximal inhibitory concentration
2. EC50: Half maximal effective concentration
3. GI50: Half maximal growth inhibition concentration
4. LD50: Lethal dose 50

All four refer to the concentration of a drug that satisfies certain conditions, and the conditions have different meanings. Some view IC50 and GI50 as the same thing, so let's look at each definition to understand why.

1. IC50
It refers to the maximum concentration at the moment when the enzyme/protein activity of the cell drops in half when the drug is administered. Here, the index indicating the activity of the cell may be an enzyme or a protein, so the value of the IC50 may vary slightly from experiment to experiment.

2. EC50
It refers to the maximum concentration of a drug that can show about half of the maximum effect that the drug can show when the drug is administered. It is also called EC50 or effective dose (ED50).

3. GI50
It refers to the maximum concentration at the moment when the cell proliferation is halved when the drug is administered.

4. LD50
It refers to the concentration of a drug in which half of the cells are killed when the drug is administered.