Intro To Parmakokinetics Flashcards
What is pharmacokinetics
The mathematical analysis of the time courses of the process of ADME of a drug administered
Pharmaco
Drugs
Kinetics
Rate
DMPK
Drug metabolism and pharmacokinetics
Distribution?
Description of where in the body the drug goes after administration and absorption
Absorption?
Process of gettting a drug from delivery site to the bloodstream
%absorption
Amount absorbed compared to amount administered
Metabolism?
how the body chemically changes foreign compounds so
that they can be more easily removed from the body
Elimination?
how the body removes drugs or metabolites
What did Paracelsus say
“All drugs are poisons,
it is just a matter of
the dose”
Pharmacokinetics and pharmacodynamics
Pharmacokinetics : how the body handles the drug
Pharmacodynamics: how the drug affects the body
What does pharmacokinetics allow
• Allows comparison of:
- drugs
- formulations
- patients
• Allows prediction of effect of changing
- dose
- dose frequency
- route of administration
Therapeutic window
Balance between therapeutic response and adverse effects. The amount of drug exposure is same
Non-adherence to medications
Major source of variability in drug therapy
Sites of measurement
- blood plasma
- blood serum
- whole blood
- breath
- milk
- urine
Plasma % of blood
55
Buffy coat % of blood
<1
Erythrocytes % of blood
45
Drug distribution and elimination are dependant on……
The unbound concentration
Extravascuar routes o administration for systemic drug delivery
Via alimentary Canal = buccal, oral, rectal, sublingual
Other routes = inhalation, intramuscular, intranasal, subcutaneous, transdermal
What is systemic circulation
carries oxygenated blood from the left ventricle, through the arteries, to the capillaries in the tissues of the body.
Pulmonary ciculation
is a short loop from the heart to the lungs and back again.
Systemic absorbiton
a route of administration of medication, nutrition or other substance into the circulatory system so that the entire body is affected.
Enterohepatic cycle
the movement of bile acid molecules from the liver to the small intestine and back to the liverl
pH partition hypothesis
explain the influence of GI pH and drug pKa on the extent of drug transfer or drug absorption.
Only non-ionised non-polar drugs penetrate the membrane and at equi, the conc of non-ionised species is equal on both sides but the total conc may be different
Routes of oral absorption from the gastric lumen
- Transcellular route: passive diffusion
- Transcellular route: active transporter utilisation
- Paracellular route (tight junctions)
- Lipid absorption via micelles / bile salts
- Particulate absorption via GALT: (Gut-Associated Lymphatic Tissue)
A drug must be ….. to be absorbed
Non-ionised and in solution
PKa and pH equations
pKa
pKa = pH - log [A-]/[HA]
pH = pKa + log [A-]/[HA]
Base % equation
100x(10 ^ pKa-pH / 1 + 10 ^ pKa-pH )
Acid %
100x(10 ^ pKa-pH / 1 + 10 ^ pKa-pH )
What is unbound concentration
The portion of drug that exerts a pharmacological effect
