Unit 4 Pharmacology: Pharmacodynamics Flashcards
Pharmacodynamics is the study of
the drugs effect on the body (relationship between effect site concentration and clinical effect)
On the dose response curve, the x axis (bottom axis) corresponds with
potency
define potency
dose required to achieve a given clinical effect.
define efficacy
intrinsic ability of a drug to elicit a given effect
On the dose response curve, the y axis (left) corresponds with
efficacy. the height of the plateau represents this.
what does the slope of the dose response curve tell us
how many receptor must be occupied to elicit a clinical effect
what is potency of a drug affected by
absorption, distribution, metabolism, elimination, and receptor affinity
what does a left shifted curve on the dose response curve represent
increased affinity for receptor, higher potency, lower dose required
what does a light shifted curve on the dose response curve represent
increased affinity for the receptor, lower potency, higher dose required
define ED50
dose required to achieve a given effect on 50% of the population. a measure of potency
define ED90
dose required to achieve a given effect on 90% of the population. a measure of potency
once the plateau is reached for efficacy, does additional drug produce any additional effect?
no
the higher the plateau, the _____ the efficacy
greater
what does a steep slope imply
that most of the receptors must be occupied before we observe the clinical response
name two categories of drugs that have a steep slope
volatile anesthetics and NMB’s
drugs that produce the same clinical effect but with different dosages have different
potencies
what does a full agonist mimic
an endogenous ligand
continuous administration of an agonist may do what to receptors
cause down regulation
examples of full agonist drugs include (4)
norepinephrine
propofol
dopamine
alfentanil
when a partial agonist binds to a receptor, does it active a full cellular response
no, it only partially activates a cellular response
a partial agonist is also called
an agonist antagonist
example of a partial agonist drug includes
nalbuphine
what happens when an antagonist binds to a receptor
it prevents an agonist from binding to it. does not tell the cell to do anything
do antagonist drugs have efficacy
by definition, they do not have efficacy
continuous administration of an antagonist may do what to receptors?
cause up regulation
if a patient receives a competitive antagonist, the dose response curve for the agonist shifts to the
right
define the effect of an inverse agonist at the receptor site
binds to the receptor and causes an opposite effect to that of a full agonist
define the efficacy of an inverse agonist
it has negative efficacy
give an example of a drug that is an inverse agonist
propanolol (binds to and activates B1 but decreases cAMP)
administering drugs together: addition
effects of two drugs given at same time are added to each other. (morphine and hydromorphone, ASA and ibuprofen)
administering drugs together: synergism
effect of two drugs given at same time is greater than the sum of the individual effects (prop and midaz, levodopa and carbidopa)
administering two drugs together: potentiation
effect of one drug is enhanced by a drug that has no effect on its own (probenecid and PCN)
administering two drugs together: antagonism
simultaneous administration of one drug negates the effect of a second drug (midaz and flumazenil, fentanyl and naloxone)
how to calculate therapeutic index
divide LD50 by ED50
ex)LD1500mg, ED125mg. 1500/25= TI 12
define TD50
dose that will produce toxicity in 50% of the population
a racemic mixture contains how many enantiomers
2 enantiomers in equal amounts
define stereochemistry
study of the three dimensional structure of molecules
define chirality
a division of stereochemistry. deals with molecules that have a center of 3D asymmetry.
a molecule with one chiral carbon will exist as how many enantiomers
two
define enantiomer
chiral molecules that are non superimposable mirror images of one another
