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19 Cards in this Set
- Front
- Back
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What does Km reflect?
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Affinity of the enzyme for the substrate
The lower Km is, the higher the affinity is |
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What is the main determinant of Vmax?
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Enzyme Concentration
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Equation relating Vmax and Km?
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Km = [S] at 1/2 Vmax
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What do the intercepts represent on the graph with y-axis of 1/V and x-axis of 1/[S]? slope =?
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y intercept = 1/Vmax
x intercept = 1/-Km slope= Km/Vmax |
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When the graph has y-axis of 1/V and x-axis of 1/[S], what do competitive vs. noncompetitive inhibitors do to the line?
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w/ a competitive inhibitor the 1/Vmax stays the same, but the 1/Km is decreased (Km inc). So the lines will cross
The Noncompetitive inhibitor line will have the same x-intercept (1/Km), but the y intercept will increase (Dec Vmax) |
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COMPETITIVE VS NOMCOMPETITIVE INHIBITORS
effect of increasing [S]? |
CI: inc [S] overcomes inhibition
NCI: inc [S] doesn't overcome inhibition |
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What does Volume of Distribution (Vd) =?
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amount of drug in body/plasma drug concentration
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So what does low, medium, and high Vd represent?
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Low (4-8L)means that the majority of the drug is distributed in the blood
Medium means the drug distributes some into extracellular space or body water High means the drug distributes into the tissue so there isn't much in the plasma |
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How many half lives does it take a drug being steadily infused at a constant rate to reach 94% of its steady state?
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4 half lives
(50%-->75%--->87.5%--->93.75%) |
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How do you calculate the Loading Dose?
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Target Plasma Concentration X (Vd/Bioavailability)
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What is the bioavailability equal to if drug is given by IV?
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1
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What happens to loading dose and maintenance dose if there is impaired renal or hepatic fxn?
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Loading dose remains unchanged, but maintenance does decreases
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What is the difference between zero-order drug elimination and first-order?
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0-order = rate of elimination is constant regardless of drug concentration
first-order = rate is proportional to drug concentration |
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3 examples of Zero-Order Eliminated Drugs?
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Phenytoin
Ethanol Aspirin |
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Difference between Phase I and II metabolism?
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Phase I (reduction/oxidation/hydrolysis)usually yields often active metabolites.
Think P-450 Phase II (acetylation/glucuronidation/sulfation) Inactive metabolites excreted renally |
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Efficacy vs Potency?
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Efficacy = max effect a drug can produce
Potency = amount of drug needed for a given effect |
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Effect of competitive and noncompetitive anatagonists on the efficacy and potency of drugs?
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A competitive antagonist will decrease potency, but not efficacy
A noncompetitive antagonist decreases efficacy |
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how do you calculate Therapeutic Index?
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Median Toxic Dose/Median Effective Dose
LD50 / ED50 Safer drugs have a higher TI |
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