Unit 2 - Pharmacodynamics, AAEPA, Dose Response Curve, Window Flashcards
What is affinity?
Strength of the binding between a drug and its receptor
What is efficacy?
The ability of a drug to elicit the maximal biological effect.
Determined mainly by the nature of the drug and receptor and its associated effector system.
Can be measured with a graded dose-response curve - not with a quantal dose-response curve.
What is potency?
Denotes the amount of drug needed to produce a specified effect.
On a dose-response curve, the drug that has the lowest EC50 is the most potent.
ED50 is the dose at which 50% of the popuation or sample manifests a given effect; used with quantal graphs
Measure of potency is effective dose to treat 50% of people
What is Kd?
the ratio of breakdown
Kd = K-1/K1
What is K1?
Rate of binding/attachment
What is Ki?
Give some examples of sites of drug action
enzymes, ion channels, neurotransmitter transport systems, nucleic acids, receptors
What is a receptor?
Specific chemical constituent of the cell with which a drug interacts to produce its pharmacological effects.
Normally a protein or glycoprotein that sits on the cell surface.
What are the 2 forms of receptors?
Active Ra and Inactive Ri
What is a second messenger?
Molecules that convey messages from the first messenger to the target organ.
Effect of drug can only happen after the drug binds to the receptor.
Which of the following is responsible for selectivity of drug action?
A. Receptor
B. Second messenger
C. Neurotransmitter
A. Receptor
What do receptors mediate?
Pharmacological agonists and antagonists
When a drug binds to its receptor, it forms a…
drug-receptor complex
Low affinity
slow formation and rapid breakdown
High affinity
Rapid formation and slow breakdown
What is K-1?
Rate of letting go/breakdown
Drugs with a high rate of dissociation (K-1) and a low rate of formation (K1) will have a ______ dissociation constant
High - drug does not bind well to its receptor
Drugs with a low rate of dissociation (K-1) and high rate of formation (K1) will have a _____ dissociation constant
low - binding of drug and receptor is strong
What is a ligand?
something that binds to a receptor site on a target protein
ED50
Effective dose of drug to treat 50% of people
What does an antagonist do at the organism level?
Bind to same site as the endogenous ligand but do not produce the same signal as the endogenous ligand.
What is reversible antagonism?
Competitive (antagonist binds to same site as agonist in a reversible manner - potency affected, not efficacy) and non-competitive (binds to site other than receptor for agonist, yet keeps the agonist from having an effect - reduces maximal response that an agonist can produce; efficacy and potency affected)
What is irreversible antagonism?
binds to same site but with very high affinity; dangerous; dissociates slowly or not at all from receptor
Maximal efficacy reduced, no change in agonist activity at unoccupied receptors
Dose-response curve shifts to the right
What is physiological antagonism?
actions of a substance that counteracts the physiological effects of a drug
nothing to do with competition for receptor sites or binding sites
counteracts the physiological effects of the drug
