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Pharmacodynamics
study of the biochemical and physiologic effects of drugs and the molecular mechanisms by which those effects are produced.
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Dose Response Relationship
relationship between the size of an administered dose and the intensity of the response produced
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What does it mean that the dose response relationship is "graded?"
patients response gets more intense with increased dosage
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Maximal Efficacy
largest effect a drug can produce
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Relative Potency
- the amount of drug given to elicit an effect
- a potent drug gives its effects in low doses
- Drug A can be more effective than drug B even though drug B may be more potent.
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What are arguably the most important receptors?
hormones, neurotransmitters, and other regulatory molecules.
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What are the 4 primary receptor families?
- 1,Cell membrane–embedded enzyme.
- 2, Ligand-gated ion channel.
- 3, G protein–coupled receptor system (G = G protein).
- 4, Transcription factor.
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Selectivity
highly desirable characteristic of a drug, in that the more selective a drug is, the fewer side effects it will produce
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What are 2 instances that a drug will be non selective?
- when a drug interacts with a receptor type that regulates multiple processes
- when a drug interacts with multiple receptors
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Affinity
- Strength of attraction between its drug and receptor
- *drugs with high affinity are very potent
- *drugs with high affinity are effective in low doses
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Intrinsic activity
- ability of a drug to activate its receptor upon binding
- *Drugs with high intrinsic activity have high maximal efficacy
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Agonists
- Drugs that mimic the body's own regulatory molecules
- agonists activate the receptor
- have high affinity
- have high intrinsic activity
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Antagonists
- Drugs that block the actions of endogenous regulators are called antagonists.
- Lack of intrinsic activity results in lack of receptor activity
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The effect of a antagonist is determined by
how much agonist is present
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What are competitive antagonists?
- produce a receptor blockade by competing with agonists.
- the receptor is occupied by whichever agent is in higher concentration.
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Partial Agonist
- an agonist with moderate intrinsic activity.
- Maximal effect is lower than a full agonist
- can act as agonists (if no full agonist is present) & antagonists (if a full agonist is present)
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Desensitization
(Refractoriness) results from continuous exposure of cell receptors to an agonist
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Hypersensitivity
Results from continuous exposure of cell receptors to antagonist
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Average effective dose
(ED 50) dose required to produce a defined therapeutic response in 50% on the population.
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Therapeutic Index
ED50:LD50 ratio between average effective dose & average lethal dose
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Wide Therapeutic Index
Narrow Therapeutic Index
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