Page 77 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

 Clearance is equal to the rate of elimination divided by the (arterial) drug

concentration before drug passes through the organ of elimination (CA):

( −
)
=

 The ratio of the rate of elimination to the rate at which drug enters an organ is a

dimensionless term that is called Extraction ratio (E).



=

)
( −
=

( −
)
=

 The extraction ratio quantifies the efficiency of an organ with respect to drug

elimination:

 If an organ is incapable of eliminating the drug, CA = CV, and the extraction

ratio will be zero (E= 0).

 If, however, the organ is so efficient in metabolizing or eliminating the drug

that CV = 0, then the extraction ratio approaches unity (E=1).

 The extraction ratio of a drug will be a number between 0 and 1.

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