Extraction ratio
Extraction ratio is a term used in pharmacology and physiology to describe the proportion of a drug that is removed from the blood during its passage through an organ. It is often represented by the symbol E.
Pronunciation
Extraction ratio is pronounced as /ɪkˈstrækʃən ˈreɪʃioʊ/.
Etymology
The term "extraction ratio" is derived from the English words "extraction" and "ratio". "Extraction" comes from the Latin word "extractionem", meaning "a drawing out", and "ratio" comes from the Latin word "ratio", meaning "reason" or "calculation".
Definition
The extraction ratio (E) of a drug is defined as the fraction of the drug that is removed from the blood during its passage through an organ. It is calculated by the formula:
E = (C_in - C_out) / C_in
where C_in is the concentration of the drug in the blood entering the organ, and C_out is the concentration of the drug in the blood leaving the organ.
Related Terms
- Clearance: The volume of blood cleared of a substance per unit time.
- Bioavailability: The fraction of an administered dose of a drug that reaches the systemic circulation.
- First-pass effect: The phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation.
- Hepatic extraction ratio: The fraction of a drug that is removed from the blood by the liver during its first pass through the organ.
See Also
External links
- Medical encyclopedia article on Extraction ratio
- Wikipedia's article - Extraction ratio
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