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PHRD5915 Drug Design Lecture 10 - Pharmacodynamics
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function of antagonist
prevents agonist from binding to the receptor
M1 expressing tissue
parietal cells
M2 expressing tissue
nerve terminals
M3 expressing tissues
smooth muscle
N
N
expressing tissue
post ganglionic cell bodies
N
M
expressing tissue
skeletal muscle cells
occupation theory
receptor is activated as long is it is occupied by the agonist
rate theory
frequency of interaction between agonist & R dictates R activation (in freq -> inc response)
an inverse agonist has a higher affinity for the receptor in the _______ state.
inactive
agonist receptor affinity/actions can be modulated allosterically by... (3)
1) other membrane-assoc'd proteins
2) agents binding at other sites on the R
3) intracellular proteins (eg G-proteins)
binds to a site adjacent to the R & decreases ability of R to be activated by agonist
non-competitive antagonist
partial agonist ______ (do/don't) have spare receptors
DON'T
receptors usually ID'd using irreversible inhibitors
spare receptors
receptor-independent drug mechanisms (2)
1) inhibition of biosynthetic/degradative enzymes
2) binding agents
physostigmine MOA
cholinesterase inhibitor decreases ACh metabolism to inc cholinergic responses
cholestyramine resin MOA
binds cholesterol to decrease GI absorption
Sugammadex MOA
binds steroidal paralytic agents to inc speed of recovery from paralysis
tachyphylaxis
receptor desensitization
tachyphylaxis occurs as a result of...
1) R number
2) R-effector coupling
pharmacokinetic tolerance
repeated exposure to a drug leads to increased induction of metabolic enzymes
pharmacodynamic tolerance
repeated exposure to drug leads to change in signal transduction pathways or other adaptive responses (reduced responsiveness)
additive effect
the effect of 2 drugs is equal to the sum of the individual effects (eg alcohol & barbituates)
synergistic effect
the effect of 2 drugs is greater than the sum of their individual effects (eg sulfamethoxazol & trimethoprim)
potentiation
a drug which alone has not effect enhances the potency of a drug which does not have an effect (eg penicillin & probenecid)
functional antagonism
effect of one agonist opposes the effect of another agonist (on different tissues)
median effective dose (ED50)
dose of drug at which 50% of individuals demonstrate the desired therapeutic effect
what does ED50 provide a measure of? (2)
1) clinical potency
2) therapeutic selectivity
median lethal dose (LD50)
dose of drug causing deaht in 50% of subjects
therapeutic index (TI)
provides an estimate of the margin of safety (inc TI -> inc margin of safety)
physiological antagonism
effect of one agonist opposes the effect of another agonist on different tissues
Author
daynuhmay
ID
274101
Card Set
PHRD5915 Drug Design Lecture 10 - Pharmacodynamics
Description
Pharmacodynamics
Updated
5/12/2014, 8:22:05 AM
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