Pharmacokinetics
Drugs movement through the body.
What the body does to the drug.
Pharmacokinetics
Absorption
Distribution
Metabolism
Excretion
Absorption
•The process by which drug proceeds from
the site of administration to the site of measurement (blood stream) within the
body.
•Necessary for the production of a
therapeutic effect.
•Most drugs undergo GIT absorption.
The Process
•Absorption relies on
–Passage
through membranes to reach the blood
–passive
diffusion of lipid soluble species.
Membranes
•Types
of Membranes:
•Cell
Membranes
•Walls
of Capillaries
•Blood/Brain
Barrier
•Placental
Barrier
Three ways to get in!
•Direct penetration of the membrane
•Protein channels
•Carrier proteins
Lipid Soluble Drugs
•Lipid soluble drugs are able to dissolve
in the lipid layer of the cell membrane
•No energy expended by the cell
•Passive diffusion
Protein Channels
• Most drug molecules are to big to pass in
to the cell via the channels – small ions such as Na+ and K+ use the protein
channels but their movement is regulated by gating mechanisms – only small
amounts allowed.
Carrier Proteins
•Molecule needs to bind with a protein
that will transport it from one side of the cell membrane to another – a drugs
structure determines which carrier will transfer it.
Anatomy of the intestines
Absorption at brush border cells
•Passive transcellular thought to be major route
•Non-charged
compounds diffuse best
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