Pharm principles Flashcards
What is Km?
The amount of substrate needed to get to 1/2 Vmax
What is Vmax?
Max velocity of enzymatic reaction. Directly proportional to enzyme concentration.
What is the relation ship between Km and affinity?
Inversely proportional; w/ small Km, not much substrate is needed to achieve 1/2 vmax –> high affinity
w/ large Km, more substrate is needed to acheive 1/2 v max –> lower affinity
On a Lineweaver Burk plot, what is the y intercept
1/Vmax
What does a higher y intercept on a Lineweaver Burk plot mean?
Lower V max.
On a Lineweaver Burk plot, what is the x intercept
1/Km
What does a x intercept closer to 0 on a Lineweaver Burk plot mean?
Higher Km, lower affinity
On Lineweaver burk plots, what do reversible competitve inhibitors look like?
Inhibitor has steeper slope with higher Km(lower affinity),, will cross the regular line at the v/max.
On Lineweaver burk plots, what do noncompetitve inhibitors look like?
Higher y intercept (lower vmax), lines do not cross. Will have same Km as regular line.
How do reversible competitive inhibitors work?
Bind active site of enzyme. Can be overcome by increase in substrate concentration.
What is the effect of reversible competitive inhibitors on Vmax /efficacy? What is efficacy
Unchanged.
Efficacy is the maximum effect a drug can produce regardless of dose.
What is the effect of reversible competitive inhibitors on Km /potency? What is potency?
Increases Km (lowers affinity); more substrate needed to reach half max effect. Potency is amount of drug needed to produce an effect.
How do irreversible competitive inhibitors work?
Bind active site but cannot be overcome; effectively eliminates available enzymes.
What is the effect of irreversible competitive inhibitors on Vmax /efficacy?
Decreases Vmax/efficacy because it has effectively eliminated enzymes, thus decreasing the max effect possible at any dose.
What is the effect of irreversible competitive inhibitors on Km /potency?
Unchanged.
How do noncompetitive inhibitors work?
Do not resemble substrate. Do not bind active site. Cannot be overcome by more substrate. Effectively reduce enzyme availability.
What is the effect of noncompetitive inhibitors on Vmax /efficacy?
Decreases Vmax/efficacy because it has effectively eliminated enzymes, thus decreasing the max effect possible at any dose.
What is the effect of noncompetitive inhibitors on Km /affinity?/potency?
unchanged
What is Vd?
Volume of distribution = amount of drug in body/plasma drug concentration.
What is the distribution of large charged molecules?
Low, blood only. Usually protein bound.
What is the distribution of small hydrophilic molecules?
Medium, ECF as well.
What is the distribution of small hydrophobic/lipophilic molecules?
High. Dist in all tissues including fat.
What is the definition of clearance?
Volume of plasma cleared up drug per unit time.
What is the equation for clearance?
rate of elim/plasma drug concentration.
aka Vd * elimination constant
