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33 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Define Pharmacodynamics
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Field of study that deals with the relationship between plasma concentration of a drug and the response obtained
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Define affinity
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Ability of a drug to bind to a receptor; on a graded dose-response curve, the nearer the curve is to the y axis, the greater the affinity (affinity deals with drugs acting on the same receptor)
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Define efficacy
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How well a drug produces a response; on a graded dose-response curve, the height of the curve represents the efficacy
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Define potency
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The amount of drug required to obtain a desired effect; on a graded dose-response curve, the nearer the curve is to the y axis, the greater the potency
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Will the curves for two drugs acting on the same receptor be parallel or nonparallel to each other on a graded dose-response curve
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Parallel
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Will the curves for two drugs acting on different receptors be parallel or nonparallel to each other on a graded dose-response curve
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Nonparallel
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Define agonist
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A drug that binds to a receptor, alters its conformation, and activates that receptor’s function
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Define full agonist
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An agonist capable of producing a maximal response
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Define partial agonist
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An agonist incapable of producing a maximal response; less efficacious than a full agonist
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Define antagonist
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A drug that binds to a receptor and prevents activation of a receptor
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Define competitive antagonist
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An antagonist that competes with an agonist for the same receptor site; graded dose-response curve will be shifted to the right (parallel) thus decreasing the agonist’s potency (and affinity); maximal response will not be affected
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Define noncompetitive antagonist
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An antagonist that acts at a different site from the agonist yet still prevents the agonist from activating its receptor; potency not affected; maximal response will be decreased; causes a nonparallel shift to the right on a graded dose-response curve
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None
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What happens when a partial agonist is added in the presence of a full agonist
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The response of the full agonist is reduced; partial agonist is acting as an antagonist
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How does a competitive antagonist affect Affinity (1/Km) of agonist
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Decreased (thus Km will increase as it is inversely proportional to affinity)
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How does a competitive antagonist affect maximal response (Vmax) of agonist
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No change
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How does a noncompetive antagonist affect the affinity (1/Km) of agonist
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No change
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How does a noncompetivie antagonist affect the maximal response (Vmax) of agonist
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Decreased
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Will increasing the dose of an agonist completely reverse the effect of a competitive antagonist
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Yes
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Will increasing the dose of an agonist completely reverse the effect of a noncompetitive antagonist
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No
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Define pharmacologic antagonism
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Antagonist and agonist compete for the same receptor site
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Define physiologic antagonism
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Two different types of agonists acting at different receptors causing opposite responses, therefore, antagonizing each other (acetylcholine activating an M receptor to cause bradycardia is antagonized by norepinephrine acting at a beta receptor to cause tachycardia)
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Define chemical antagonism
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Response to a drug is antagonized by another compound that binds directly to the effector drug (digoxin is antagonized by Digibind which binds directly to digoxin and not its receptor)
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Define potentiation
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When one agonist enhances the action of another compound (benzodiazepines and barbiturates potentiate the effect of gamma-aminobutyric acid [GABA] on its receptor); graded dose-response curve is shifted to the left
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What is a quantal (cumulative) dose-response curve
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Curve showing the percentage of a population responding to a given drug effect vs. dose of drug given (or log of dose); allows you to visualize intersubjective variability regarding drug response in graph form
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What is ED50
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Estimation of the effective dose in 50% of a population; the dose at which 50% of the population will respond to the drug
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Can you obtain the ED50 from a graded (quantitative) dose-response curve
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No (this curve does not represent a population of individuals)
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Can you obtain the ED50 from a quantal (cumulative) dose-response curve
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Yes (this curve represents a population of individuals)
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What is TD50
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Estimation of the toxic dose in 50% of a population; the dose at which 50% of the population will have toxic effects from the drug
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What is LD50
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Estimation of the lethal dose in 50% of a population; the dose at which 50% of the population will die from the drug
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What is therapeutic index (TI)
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The relative safety of a drug by comparing the ED50 to either the TD50 or LD50; the safer the drug the “wider” the TI meaning the TD50 or LD50 is much greater than the ED50; drugs with a “narrow” TI have their TD50 or LD50 close to the ED50
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How do you calculate TI
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TI = TD50/ED50 or LD50/ED 50
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What is a narrow therapeutic index (NTI)
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Drugs with a NTI usually have a TI<2
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List some examples of drugs with a NTI
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Carbamazepine; digoxin; levothyroxine; lithium; phenytoin; theophylline; valproic acid; warfarin
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