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15 Cards in this Set
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- 3rd side (hint)
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What is pharmacokinetics
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Absorption
Distribution Metabolism Excretion |
ADME
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Volume of distribution
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Space or compartment in which a drug distributes. Greater Vd means more extensive distribution into tissues. Vd depends on drug penetration into tissues, proteing and tissue binding.
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Clearance
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Measure of removal of drug from a volume of plasma in a given unit of time. Determined by blood flow and extraction ratio.
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First order vs zero order elimination.
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Most drugs are eliminated by first order process. First order elimination is a constant proportion over time, zero order is a constant amount over time.
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Types of drug interactions
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Altered absorption
Altered protein binding Altered renal excretion Inhibition of metabolism Induction of metabolism |
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Protein binding
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Extent of binding influences drug distribution and elimination. Only free drug can diffuse through capillary wall; produce pharm. effects; undergo metabolism/excretion.
Albumin is the most important protein in binding, binds both acidic and basic drugs. |
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blood brain barrier permeability
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more permeable for drugs that are lipophilic, low ionization, non protein bound, but also more permeable in certain disease states
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metabolism by CYP450 enzyme
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occurs in liver and often either inserts a reactive chemical group or unmasks a reactive group to allow for conjugation
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metabolism by conjugation
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reactive group on drug/metabolite is combined with:
glucuronic acid sulfate glycine acetate |
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glucuronic conjugation
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Most common conjugation, occurs in liver, metabolized in liver and excreted in bile (subject to enterohepatic recirculation). This is non-saturable (no limit in amount that can be metabolized)
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sulfate conjugation
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Second most important conjugation. It is saturable (limits to amount that can be handled). Results are highly polar and readily excreted in urine.
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Sites of metabolism
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Liver is most important, also occurs in lungs, kidneys, intestinal mucosa and skin
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First pass metabolism
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Removal and metabolism from the portal circulation by the liver.
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Factors affecting renal excretion
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Volume of distribution
Protein binding GFR Tubular fluid pH Back diffusion of un-ionized form of drug Active tubular secretion |
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Biliary excretion
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Most compounds excreted through bile enter the intestine, are absorbed into the blood and excreted by the kidneys. Some are excreted in feces.
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