Pharmacokinetics and Pharmacodynamics I Flashcards
(25 cards)
In the Michaelis-Menten equation, what is Km?
[S] at 1/2 of Vmax (p.226)
How does the value of Km relate to enzyme affinity for its substrate?
Higher Km means lower affinity; lower Km means higher affinity (p.226)
How does Vmax relate to enzyme concentration?
Vmax is directly proportional to enzyme concentration (p.226)
Describe the shape of the curve in an enzymatic reaction that follows Michaelis-Menten kinetics.
Hyperbolic curve (enzymatic reactions with positive cooperativity have a sigmoid curve) (p.226)
What does a Lineweaver-Burk Plot represent?
1/[S] vs 1/V (p.226)
What is the slope of the line in a Lineweaver-Burk plot?
slope= Km/Vmax (p.226)
What does the Y-intercept of a Lineweaver-Burk plot represent?
1/Vmax (p.226)
What is the relationship of the position of the Y intercept and Vmax in a Lineweaver-Burk plot?
The greater the Y intercept, the lower the Vmax (p.226)
What does the X-intercept of a Lineweaver-Burk plot represent?
=1/(-Km) (p.226)
What is the relationship of the position of the X intercept and Km in a Lineweaver-Burk plot?
The further to the right the X intercept (i.e. closer to the Y axis), the greater the value of Km and the lower the enzyme affinity (p.226)
In a Lineweaver-Burk plot, how do you distinguish a competitive inhibitor from a noncompetitive inhibitor?
Competitive inhibitors cross the line of the uninhibited reaction; non-competitive inhibitors do not cross the line (p.226)
Compare competitive and noncompetitive inhibitors in terms of the resemblance of the inhibitor to the substrate.
Competitive inhibitors resemble the substrate; non-competitive inhibitors do not (p.226)
Which types of enzymatic inhibitors can be overcome by increasing substrate and which ones can not?
Competitive inhibitors can be overcome by increasing [S]; non-competitive inhibitors can not (p.226)
Compare competitive and noncompetitive inhibitors in terms of binding to the active site.
Competitive inhibitors bind the active site; non-competitive inhibitors do not (p.226)
What is the effect of a noncompetitive inhibitor on Vmax?
Decreases Vmax (p.226)
What is the effect of a competitive inhibitor on Vmax?
No effect on Vmax (p.226)
What is the effect of a noncompetitive inhibitor on Km?
No change on Km (p.226)
What is the effect of a competitive inhibitor on Km?
Increases Km (p.226)
What pharmacodynamic property is primarily affected by competitive inhibitors?
Decreased potency (p.226)
What pharmacodynamic property is primarily affected by a non-competitive inhibitor?
Decreased efficacy (p.226)
What is bioavailability (F)?
The fraction of an administered drug that reaches systemic circulation unchanged (p.227)
What mode of drug delivery has 100% bioavailability?
IV dosing (p.227)
What is the volume of distribution of a drug?
A theoretical fluid volume required to maintain the total absorbed drug amount at the plasma concentration (p.227)
What conditions may alter the volume of distribution of plasma protein-bound drugs?
Liver and kidney disease may decrease protein binding and increase drug volume of distribution (p.227)
