Dose Curves Flashcards
What is the dose response function
expresses the relationship between the dose administered and the response observed
How are does response functions determined
groups of individuals are administered a different amount of a drug in question and the response is measured; the test groups are compared to a control group given a placebo
what is a placebo
an inactive drug looks like a medication but is not
what is the placebo effect
attributed to psychological factors; expectations of drug effects and prior experiences
what is a double blind procedure
control measure for bias; neither the subject or researcher knows whether the substance given is the medication or placebo
What is a dose response curve
graph comparing the size of response to the amount of drug
x-axis: dose of drug
y-axis: effect of the drug
what is the difference between dose and concentration
concentration is the amount of molecule of interest in its vehicle
Dose refers to the amount of drug administered to a person
what are the components of a dose response
1) Dose-plasma concentration relationship
2) Plasma concentration-response relationship
what are the advantages of plotting a dose response curve on a log scale
1) full range of doses can be observed
2) easier to illustrate the effects/interactions of agonists and antagonists
What is Kd?
ratio of drug receptor dissociation
[drug][receptor] / [drug-receptor complex]
What does it mean if a drug has a high Kd
weak interaction, low receptor affinity
what does it mean if a drug has a low Kd
strong interaction, high receptor affinity
What happens as the concentration of a free drug increases in terms of Kd
the percentage of bound receptors increases
What is Emax
maximal observed effect of a dose of a drug
how do you calculate E?
E= Emax * [D} / Kd + [D}
what is a graded dose response curve
measured in a single biologic unit
continuous scale (increased dose = increased effect)
relates dose to intensity of effect
what is a quantal dose curve
population studies
all or none pharmacologic effect (did drug work? yes or no)
relates dose to frequency of effect
what is the slope factor of a dose response curve
increase of slope illustrates how much change in effect a little increase of dosage will have
what is a curvilinear or biphasic function of a dose curve
increasing doses are associated with increasing responses and then the effect decreases
what is the therapeutic window
the drug doses in which a therapeutic response is obtained
what are the characteristics of drugs that can be derived from dose response curves
threshold dose
maximal response
what is the threshold dose
the smallest dose that produces a measurable response
what is the maximal response
greatest degree of a given response that can be achieved with that drug
what is the ED50 of a drug
effective dose for half of the subjects tested /
the dose that produces 50% of max effect
what is the LD50
lethal dose for half of the subjects tested
what is a side effect
unintended effects that accompany therapeutic effects
what is the therapeutic index
a measurement of a drugs relative safety
how is therapeutic index calculated
ratio of LD50 to the ED50
What therapeutic index of a drug is considered safe
100+
what therapeutic index of a drug is considered unsafe
less than 10
what is efficacy of a drug
refers to how well a drug can produce a given effect
what is the potency of a drug
refers to how much of a drug is needed to produce a given effect
i.e. the less of a drug required to produce an effect = greater potency
what is antagonism
potency or efficacy of a drug is reduced in the presence of another drug
what is synergism
two drugs together are more potent and/or efficacious than either drug alone
what are the two different kinds of synergism
additive and potentiation
what is additive synergism
when two drugs are given together and it increases the potency and efficacy of both
what is potentiation
Drug that has no effect increases potency of another drug when given in combination
what is competitive antagonism
antagonist binds to the same binding site on receptor as drug
how can competitive antagonism be overcome
can overcome by increasing the concentration of the drug
what does competitive antagonism do to the dose response curve
shifts curve to the right
what is a partial agonist
a drug that binds to a receptor at its active site but produces only a partial response
what is an inverse agonist
produce a response below the baseline
what is the difference between an inverse agonist and a competitive agonist
competitive agonist has no effect in the absence of agonist, whereas an inverse agonist deactivates receptors that are constitutively active in the absence of agonist
What is orthostatic binding
ligand binds to the agonist binding site
what is allosteric binding
ligand binds to alternative binding site
what is positive modulation (PAMS)
increase the effect of agonist binding
what is negative modulation (NAMS)
decrease effect of agonist binding
