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NURS 8024 Pharmacokinetics/Pharmacodynamics TERMS AND DEFINATIONS STUDY GUIDE.
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NURS 8024 Pharmacokinetics/Pharmacodynamics TERMS AND DEFINATIONS STUDY GUIDE.
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NURS 8024Pharmacokinetics/Pharmacodynamics
TERMS AND DEFINATIONS STUDY
GUIDE.
Lipophobic
✔✔AKA hydrophilic
Unable to cross lipid rich cell membranes
Poorly absorbed
Lipid: aqueous partition coefficient
✔✔Determines how easily the molecule moves between aqueous and
lipid media
Partition coefficient
✔✔Ratio of lipid solubility to aqueous solubility
If higher, substance is more membrane soluble
Factors influencing GI absorption
✔✔Blood flow: intestinal blood flow > stomach blood flow
pH: pH of stomach influences absorption (PPI/H2)
Surface area: intestinal surface microvilli
Contact time with absorptive surface: PSNS causes increased rate of gastric
emptying & less contact time; SNS causes decreased rate of gastric
emptying & more contact time; food affects this
,Bioavailability
✔✔Fraction of chemically unchanged drug that reaches systemic
circulation; affected by first-pass metabolism, solubility, chemical
instability, nature of the drug formation (chemistry, molecule size, entering
coatings, etc.)
Ideal drug for absorption
✔✔Largely hydrophobic/lipophillic, but with some solubility in aqueous
solution
Bioavailability: Enteral/Parenteral administration
✔✔Bioavailability for IV drugs is high right away; PO medication
bioavailability is never quite as high d/t first-pass effect
Bioequivalence
✔✔Similar drugs are bioequivalent if they have comparable
bioavailability and similar time to achieve peak plasma concentration
Therapeutic equivalence
✔✔Similar drugs are deemed therapeutically equivalent if comparable
efficacy and safety
Clinical effectiveness is dependent on serum drug concentrations and the
time it takes to reach peak drug concentrations
Two drugs that are bioequivalent may not be therapeutically equivalent
Used in substituting drugs for formularies
Drug distribution
✔✔Process in which drug reversibly leaves bloodstream and enters
interstitium and/or cells
, Drug delivery depends on...
✔✔Blood flow
Capillary permeability
Plasma protein binding
Drug structure
Hydrophobicity
Drug distribution: Blood flow
✔✔Wide variance d/t unequal distribution of cardiac output; highest in
organs (heart, brain, lungs, liver, kidney, guts), lower in skeletal muscles,
lowest in adipose tissue
Drug distribution: Capillary permeability
✔✔Governed by capillary structure & chemical nature of the drug
Large slit junctions between endothelial cells of spleen and liver allow
passage of plasma proteins & thus drug molecules
Slit junctions are absent in brain: "blood brain barrier"
Lipid soluble drugs penetrate the brain by going across membrane, but
ionized or polar drugs cannot enter brain d/t lack of slit junctions
Drug distribution: Drug Structure
✔✔Chemical nature of the drug largely determines it's ability to cross cell
membranes
Hydrophobic/lipophillic drugs (no net charge, uniform electron distribution,
easier to pass through, able to dissolve in lipid cell membranes and
permeate cell surface)
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