Lecture 2 Part 2 Flashcards
how can agonists be divided?
into 2 classes based on the maximum pharmacological response that occurs when ALL RECEPTORS ARE OCCUPIED-
-partial agonist
-full agonist
true or false
partial agonists produce a lower response at full receptor occupancy than full agonists
true
true or false
emax is lower for full agonists than partial
false
emax is lower for partial agonists than full
partial agonists produce concentration-effect curves that resemble what?
resembles the concentration-effect curve of full agonist in the presence of an irreversible antagonist
______ experiments have demonstrated that partial agonists may occupy all receptor sites
Radioligand-binding experiments
what happens when partial agonists saturate all receptor sites
they still fail to produce a maximal response (compared to that of a full agonist)
TRUE OR FALSE
increasing concentration of partial agonist cannot displace a fixed conc of agonist from the receptor
FALSE - it can
true or false
partial agonists may occupy all receptor sites
true
in the presence of partial agonist, can emax be reached?
NO
partial agonists are “not as good” at activating the receptor
the response caused by a single concentration of full agonist ______with increasing concentrations of partial agonist
why?
decreases
the partial agonists are competing with the agonists to bind to the receptor. The partial agonist with increasing concentration, increasingly occupies the receptors and is “not as good” at activating them
true or false
all methods of antagonism involve interaction of drugs/endogenous molecules at a single type of receptor
FALSE
there are chemical antagonists and physiologic antagonists
explain chemical antagonists and give an example
one drug may antagonize the actions of another drug by binding to and inactivating the drug.
ex: heparin is an anticoagulant that is negatively charged.
PROTAMINE is positvely charged and can be used to clinically counteract the effects of heparin.
protamine antagonizes the effect of heparin by binding to it and making it unavailable for interaction with proteins involved in blood clot formation
what is a major side effect of heparin
excessive bleeding
what is the antidote to heparin
protamine - a chemical antagonist
antacids could be considered what kind of antagonist
chemical
physiologic antagonism takes advantage of _______ regulatory pathways
endogenous
many physiologic functions are controlled by what?
give an example
opposing regulatory pathways
ex: glucocorticoids increase blood sugar and the pancreas produces insulin to lower blood glucose levels (clinician could also administer insulin)
to oppose the hyperglycemic effects of a glucocorticoid hormone, the clinician must sometimes administer what? what is this an example of?
insulin
physiologic antagonism
GRADED dose response curves show……….
the effects on a continuous scale and the intensity of the effect is proportional to the dose
when choosing among drugs and determining the appropriate dose for a drug, what must be considered?
the drug’s POTENCY and MAXIMAL EFFECT
define potency
the concentration/dose of drug required to produce 50% of the drug’s maximal effect
-EC50/ED50
potency depends on what 2 things
the affinity of drug binding (KD)
the maximal response for that drug (efficacy)
potency depends on __ and ___
affinity (KD) and efficacy
define efficacy
the measure of an effect produced by a drug
what terms are most important to use when COMPARING DRUGS
potency and efficacy
_____ is determined by the maximal response of the drug
efficacy
when comparing the potency of drugs, what exactly are you comparing?
the EC50/ED50
what is a Quantal dose effect curve
basically just tells whether the desired effect occurred or it didn;t
explain how quantal/graded dose response curves can be used in different scenarios
graded dose response curves are limited in their application to clinical decision making bc they can’t be used if the pharmacological response is QUANTAL EVENT (either-or)
ie: prevention of convulsions, death
ALSO clinical releavance of graded dose response curve in a single patient may be limited in its application to other patients (the severity of the disease/responsiveness to the drug)
name 2 limitations of graded dose response curves
how can these problems be avoided?
-does not work for a quantal event (either/or) ie: prevention of convulsions, death
-clinical application – graded dose response curve for a single patient may not apply to all patients in that the severity of the disease and responsiveness to the drug may be different
can be avoided by determining the dose of drug required to produce an effect of specific magnitude in a LARGE NUMBER OF PATIENTS (or animals) and lpotting the cumulative frequency distribution of responders vs the log dose (GAUSSIAN NORMAL CURVE – how pts tend to respond to drugs)
________- may be used to generate information regarding the margin of safety
quantal dose-effect cirves
besides quantal dose effect curves, toxic effects of a drug on humans/animals can also be assessed by….
plotting the cumulative frequency distribution of responders vs log dose
in order for a drug to have a HIGH MARGIN OF SAFETY, the therapeutic effects should be observed at _______ doses than toxic effects
lower