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23 Cards in this Set
- Front
- Back
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What is volume of distribution (Vd) a reflection of? |
The ability of the drug to distribute itself throughout the body |
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What is the concentration of the drug in the plasma (Cp) used to approximate? |
Drug concentration at the receptors |
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What are the three pharmacokinetic phases? |
1.) Absorption into systemic circulation 2.) Distribution from blood into tissues 3.) Elimination by metabolism and/or excretion |
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What is bioavailability (F)? |
Fraction of dose that reaches systemic circulation |
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What is clearance? |
The volume of plasma from which kidneys can remove a substance per unit of time |
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What is the difference between first order and zero order elimination? |
First order elimination: Rate of elimination is proportional to concentration Zero order elimination: rate of elimination is independent of concentration |
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What are the three "constants" when calculating pharmokinetics? |
Clearance, half-life, and volume of distribution |
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How is clearance related to a substance's half-life? |
Inversely proportional: The smaller the clearance, the longer the half-life |
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How many half-lives does it take to reach steady state? |
4 half-lives |
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What is a therapeutic window? |
The concentrations between the minimum dose of therapeutic benefit and the minimum dose of toxic effects |
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What are Phase I reactions? |
Chemical changes that make compounds more hydrophilic and also provide a functional group that is needed to complete Phase II reactions |
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What enzymes mediate the majority of Phase I reactions? |
Cytochrome P450
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Which group of cytochrome P450 is responsible for over 50% of drug metabolism? |
CYP3A |
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What effect does an inducer of CYP450 have on drug metabolism? |
Speeds drug metabolism and increases the risk of inadequate treatment |
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What is the significance of CYP2D6? |
Polymorphisms in the CYP2D6 gene result in variation of enzyme functionality across individuals. |
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What is the consequence of being a "poor metabolizer"? |
Individuals will exhibit higher plasma concentrations and decreased clearance of drugs. This will result in increased pharmacologic effects of drugs metabolized by CYP2D6 |
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What are two inducers of CYP2C8-10? |
Phenytoin, Rifampin |
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What are three inhibitors of CYP3A? |
Erythromycin, grapefruit, ketoconazole |
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What is an inducer of CYP3A? |
St John's wort |
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What are Phase II reactions? |
Polar groups are added to molecules by transferases to aid in excretion |
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What are there substances that are NOT metabolized by CYP450? |
(Nor)epinephrine, acetylcholind/succinylcholine, and alcohol |
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What are four possible results of drug metabolism? |
1.) Inactivate the drug 2.) Activate the drug ("pro-drug") 3.) Generate active metabolites 4.) Generate toxic metabolites |
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What are three common drugs that use zero order elimination? |
Ethanol, aspirin, and phenytoin |
