Blood drug amount {bioavailability} relates to dose.
Brain-compartment drug concentration to blood-compartment drug concentration makes ratios {Blood-Brain Barrier penetration}.
Drug diffusion calculations {diffusivity} can measure drug-diffusion ease.
Distribution and elimination can combine {disposition, drug}.
Drugs have different concentrations in various body tissues {distribution, drug}.
Excretion {elimination, drug} uses urine and feces.
Ingested drugs affect intestinal-wall cells {enterocyte}.
Bile goes back to GI tract for recycling {enterohepatic cycling} (EHC).
Liver removes drugs from blood {intrinsic clearance} (CL).
Compounds above 500 to 700 cannot diffuse across lipid membrane {molecular weight theory}.
Percentage of orally administered drug in general blood circulation, or in urinary excretion, compares to intravenous administration {absolute oral bioavailability} {oral bioavailability}.
A vein {portal vein} carries blood to liver from GI tract.
Active or passive transport carries drug from intestine to portal vein {absorption, drug}.
Compounds absorbed from intestine {human intestinal absorption} (HIA) go to portal vein.
Intestines have contents travel rate {motility}.
Acidic or neutral drugs can diffuse across GI-tract lipid membrane, but basic drugs cannot diffuse {pH partition theory}.
Drug goes from intestine to portal vein {predicted fraction of human absorption} (Fa). Fraction is in percent.
Compounds can have good solubility in lipids {lipophilicity}.
Values {Fujita-Hansch pi value} can relate to lipophilicity.
Octanol/water partition coefficient logarithms {log P} can measure lipophilicity.
Hydrophobicity measures {molecular lipophilicity potential} (MLP) can calculate lipophilicity surface.
Lipophilic compounds can diffuse across lipid membrane {octanol-buffer partition coefficient theory}.
On brain-capillary endothelial-cell insides, proteins {P-glycoprotein} can prevent high-lipophilicity drugs from crossing BBB.
Drugs must get to sites {transport, drug} {drug transport}.
Diffusion carries molecules across membranes {passive transport}.
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Date Modified: 2022.0225