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Chapter 5 pharmaco


Pharmacodynamics the study of the biochemical and physiologic effects of drugs and the molecular mechanisms by which effects are produced
The dose- response relationship is graded. The response becomes progressively larger with increasing dosage
Maximal efficacy is the most intense effect a drug can produce
A drug with a very high maximal efficacy is not always most desirable as the intensity of the drug response must be matched to the patient's needs.
potency is defined as the amount of a drug that must be given to elicit an effect
It is important to note that the potency of a drug implies nothing about it's maximal efficacy
A receptor can be defined as any functional macro- molecule in a cell to which a drug binds to produce its effects
Binding of a drug to its receptor is usually reversible
the receptors through which drugs act are normal points of control for physiologic processes
under physiologic conditions, receptor function is regulated by molecules supplied by the body
All that drugs can do at receptors is mimic or block the body's own regulatory molecules
Because drug action is limited to mimicking or blocking the body's own regulatory molecules, drugs cannot give cells NEW functions. Only alter the rate of pre-existing capabilities.
Drugs produce their therapeutic effects by helping the body use its pre-existing capabilities to the patient's best advantage.
It should be possible to synthesize drugs that can alter the rate of any biologic process for which receptors exist
The four primary families of receptors are 1.) cell membrane- embedded enzymes, 2.) ligand- gated ion channels, 3.) G- protein- coupled receptor systems and 4.) transcription factors
Selective Drug Action is possible largely because drugs act through specific receptors
If a drug interacts with only one type of receptor and that receptor regulates just a few processes the drug will have limited effects
Selectivity does not guarantee safety
affinity the strength of the attraction between a drug and its receptor
Drugs with high affinity are very potent
intrinsic Activity the ability of a drug to activate a receptor upon binding
drugs with high intrinsic activity have high maximal efficacy
Agonist are molecules that activate receptors
Agonists have both affinity and high intrinsic activity.
Affinity and high intrinsic activity allows agaonists bind to receptors and activate that receptor after binding
Antagonists produce their effects by preventing receptor activation by endogenous regulatory molecules and drugs
Antagonists have affinity for receptors but lack of intrinsic activity prevents the bound antagonists from causing receptor activation
If no agonist is present administration of a antagonists has no observable effect
Antagonists are subdivided to two major classes noncompetitive antagonists and competitive antagonists
Noncompetitive antagonists bind irreversibly to a receptor
Competitive Antagonists Bind reversibly to a receptor
Partial agonists have only moderate intrinsic activity which meancs their maximal efficacy is lower than that of full agonists.
(desensitized) When the receptor continually exposed to an agonist,the cell... becomes less responsive
Desensitized refractory, (down regulation)
Continuous exposure to antagonists causes the cell to become hyper sensitive (super-sensitive)
Most effects from drugs results from drug receptor interactions
Other ways that drugs effects arise physical or chemical interactions with other small molecules
The dose required to produce a therapeutic response can vary substantially from patient to patient
The average effective dose (ED50) is the dose required to produce a defined therapeutic response in 50% of the population
Standard dose ED50
After a patient's response to standard dose has been evaluated, subsequent doses are altered accordingly
Because drug responses are not completely predictable, the nurse must evaluate the patient to determine if more or less of the medication has been administered.
Therapeutic Index LD50:ED50
Created by: Hoopster