Pharmacodynamics Flashcards
Kd (equilibrium dissociation constant)
Concentration of ligand producing half-maximum occupancy
Bmax
Number of available receptors
Which indicates a higher drug affinity for receptor, high Kd or low Kd?
Lower Kd indicates stronger affinity between drug and receptor
What is plotted on a Scatchard plot and what do the slope and x intercept give?
[LR]/[L] vs. [LR]. Slope = -1/Kd, X-int = BMax
Three important characteristics of the dose-response relationship
Graded, Concentration-dependent, Saturable
Potency
Concentration of ligand required to yield an effect
EC50
Concentration of drug producing a half-maximal effect
Efficacy
A measure of the maximum biological effect a drug can produce (at unlimited dose)
Emax
The maximum effect a drug can produce (a measure of Efficacy)
An x-fold increase in receptors produces what change in ED50 and what change in potency?
2x-fold DECREASE in ED50 (less drug required, now more potent). Can also be stated as a 2x-fold increase in potency
Does increasing the number of receptors impact efficacy, potency, or both?
Potency but not efficacy
On a dose response curve, which axis reflects potency and which reflects efficacy?
X axis reflects potency (more potent drugs to left), and Y axis reflects efficacy (higher efficacy drugs higher up)
Do partial agonists have reduced potency or efficacy relative to full agonists?
Reduced efficacy (cannot produce maximum response)
Do competitive antagonists affect potency or efficacy?
Potency (i.e. they shift the curve to the right, but do not reduce its maximum height)
Do non-competitive antagonists affect potency or efficacy?
Efficacy, but not potency (i.e. they make the curve less tall, but do not shift it left or right)
