M1: Ch2 Drug Receptors & Pharmacodynamics Flashcards
Chemical agent that affects the biological system in a potentially useful way. For prevention, diagnosis & treatment of illnesses.
Drug
Science of dealing w/ interactions of chemical agents & living systems
Pharmacology
Used for diagnosis of Pheochromocytoma
VGA
Chemical agent that produces harmful effects. Especially in high doses.
Poison
Drug concentration and its biologic effects. What drugs do to the body.
Pharmacodynamics
What the body does to the drug
Pharmacokinetics
Four processes occurring in Pharmacokinetics
Absorption, Distribution, Metabolism & Elimination
Formulated the latin saying “Corpora non agunt nisi fixata”
Paul Ehrlich
Chemical reaction of molecules through their interaction of basic/acidic properties
Mechanism of Action
An example of Antacid
Aluminum Magnesium Hydroxide
Other name of Aluminum Magnesium Hydroxide
Maalox
Used as an antidote in heparin overdose
Protamine Sulfate
An example of membrane surfactant which binds with ergosterol. Interferes with synthesis of fungal cell wall then destroys its integrity causing leakage.
Amphotericin B
Ability of drugs to denature protein. An example of this is
Astringent
Macromolecule component of a cell or organism that interacts with a drug and initiates the chain of biochemical events leading to the drug’s observed effects.
Receptor
Drug molecule. May interact with drug receptor & would translate to a positive reaction.
Ligands
Ability to bind
Affinity
Ultimately leads to a drug effect
Transduction of signal
Nonregulatory molecules capable of binding to receptors which will result in no detectable change in function; not completely without significance (used to determine amount of free drug in the circulation). It can be bind but unable to transduce particular signals.
Inert binding sites
Examples of Inert binding sites
Albumin & A1 Glycoprotein
Receptor Subtypes: example is xanthine oxidase
Enzymes
Interferes with action of Xanthine Oxidase. Anti hyperuricemic agent.
Allopurinol
Receptor Subtypes: Examples are Calcium channel blockers
Ion Channels
Example of Calcium channel blockers
Nifedipine, Verapamil & Daltiazem “NVD”
Receptor Subtypes: examples are alpha & beta adrenergic receptors
Membrane receptors
Alters the activity of membrane activated enzymes. G proteins.
Epinephrine
Perfect compatibility between drug molecule and receptors. Perfect fit.
Lock & Key model
Chemical Basis for D-R Interaction: weak but able to interact. More common.
Electrostatic Interaction
Examples of Electrostatic Interaction
H bonds & vdw
Chemical Basis for D-R Interaction: Important for lipid soluble drugs
Hydrophobic Interactions
Chemical Basis for D-R Interaction: Least common but strongest in all chemical reactions.
Covalent bond
An example of a drug with covalent bond which interacts with Alpha adrenergic receptors.
Phenoxybenzamine
An example of a Stereospecific drug
Carvedilol
For Alpha & Beta Adrenergic Receptors
S Carvedilol
Only for Alpha Adrenergic Receptors
B Carvedilol
Drug agonists act by binding to (occupying) a distinct class of biologic molecules with a characteristic affinity for the drug receptor.
Mass action law
Maximal response that can be produce by a drug
Emax
Concentration of drug that produces 50% maximal effect
EC50
Total concentration of receptor sites are occupied already (ex. Sites bound to the drug at infinitely high concentrations).
Bmax
Concentration of free drug at which half maximal binding has been achieved.
Kd
If Kd is low, binding affinity is
High
Dose-Response Relationship: Responses to low doses of the drug usually ______ in direct proportion of the dose.
Increase
Dose-Response Relationship: As the dose increase, it reaches a point where
No further increase in response can be achieved
Dose-Response Relationship: At low concentration, effect changes
Rapidly
Dose-Response Relationship: At higher concentration, effect changes
Gradually
Transduction process that links drug occupancy of receptors & pharmacologic response
Coupling
Maximal biologic response at a concentration of agonist that does not result in occupancy of the full complement of available receptors. Full effect was achieved but D-R binding are not fully saturated.
Spare receptors
In Spare Receptors: Non occupancy of the full complement of available receptors. EC50 is ___________.
Less than Km
Drugs that bind & activate receptors. They are the key.
Agonists
Bind and prevent agonist from binding.
Classical Antagonist
Prevent agonists from activating receptors. Binds to receptors but do not activate them.
Receptor Antagonists
The tenacity or degree of attraction of a ligand to a receptor. Probability of a molecule to bind to its receptor. Drug gets bound to the receptor.
Affinity
Quality to determine its ability to produce a biologic effect. Property relating to drug molecule to itself. What happens once the drug is bound.
Efficacy
Comparative for distinguishing which agonist has higher affinity for a given receptor
Potency
Drug that produce less than maximal activation of a receptor.
Partial Agonist
Signal Transduction Mech of Agonist: Drug structurally attach itself to ion channels. Conformational change in receptor complex. Ion channels open w/c results to a flow of permeant ion.
Direct Activation of Ion Channel
Direct Activation of Ion Channels are commonly found in
NMJ, Excitatory receptors & GABA receptors “NEG”
Receptors that commonly affects NMJ
Nicotinic Receptors
Excitatory AAs
Glycine, Aspartate & Glutamine “GAG”
Signal Transduction Mech of Agonist: Activation of ion channels. Drug attaches to receptor. Activation of G protein. G protein subunits stimulate the channel to open.
Activation of G Proteins
Example of Activation of G Proteins
M2 Cholinergic Receptors
Activation of ion channels
GS activation
Induces B1 Receptor Binding
NorEpinephrine
Activation of adenylyl cyclic, (+) cAMP, (+) Protein Kinase A which acts as a second messenger.
G protein mediated
Activation of PKC to IP3 then release of Calcium
Phospholipase C
Uses second messenger, PK-C. Increases vascular wall.
Angiotensis
Most hormones utilize this
Tyrosine Kinase
Long lasting in nature
Phosphorylation of Tyrosine Kinase
Positive Affinity, Negative Efficacy.
Antagonist
Binding to a site on the receptor protein separate from the agonist binding site and thereby preventing receptor activation without blocking agonist binding. Actions are irreversible if they do not bind covalently.
Noncompetitive Antagonism
Bind to a separate site on the receptor protein and alter receptor function without inactivating the receptor.
Allosteric modulators
Bind to the agonist binding site of a receptor
Competitive Antagonism
As the degree of antagonism increases with increasing dose of antagonist but can be overcome by increasing the dose of agonist. Agonist concentration-effect curve is shifted to the right.
Reversible competitive antagonism
By covalent bond with the receptor or by binding so tightly that the receptor is unavailable for binding of agonist. Effect of antagonist is not affected even by the increase dose of drug. Antagonist inactivates the receptor.
Irreversible competitive antagonism
Other types of Antagonism
Chemical, Pharmacokinetic & Physiological “CPP”
Effect of two drugs may be combined
Additivity
Example of Additivity
Barbiturates & Tranquilizers
Phenomenon of total effect of two or more drugs more than cumulative sum of their individual effects. Barbiturates plus Alcolohol equals ______.
Synergism. Coma.
Ability of a drug to affect a particular cell type.
Selectivity
Narrow range of action
Increase Selectivity
Broad range of action
Decrease Selectivity
Drug has only one effect on all biological systems
Specificity
Alpha 2 Selectivity
Yohimbine
Majority of the drugs are more _________ than __________.
Selective than Specific
Concentration range which a drug produces its therapeutic effect
Therapeutic window
Cumulative calculation of the population responding to a particular drug. Depicts the dose of drug and the dose that gives a minimal effect. All or none.
Quantal Dose-Response Curve
Example of a Quantal Drug-Response Curve Application
Use of Anticonvulsants
Dose that produces a toxic effect in 50% of population. Median toxic dose.
TD50
Dose that produces mortality in 50% of population. Median lethal dose.
LD50
Therapeutic dose. Dose that produces desired response in 50% of population. Median effective dose.
ED50
Ratio of the TD50 to the ED50. TD50/ED50.
Therapeutic Index
The Higher the Therapeutic Index
The safer the drug would be
The lower the EC50
The higher the Potency
Indicates a more toxic scenario
Lower Therapeutic Index