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29 Cards in this Set
- Front
- Back
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If [A] is the agonist concentration and [R] is the receptor concentration and binding is normal, [AR] = ?
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[AR] = Rt / (1 + Ka/[A])
where Rt is total receptors and Ka is the dissociation constant for A |
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When an agonist is bound to half the total receptors (Rt/2), what is the concentration of A in terms of the dissociation constant Ka?
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[A] = Ka
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Efficiency of drug binding is defined as:
A) The concentration of the drug required to produce half the maximum effect B) The maximum effect that can be produced by the drug |
B
A concentration of [AR] is multiplied by a factor e (efficiency) to define the efficiency of the drug binding. |
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Potency of drug binding is defined as:
A) The concentration of the drug required to produce half the maximum effect B) The maximum effect that can be produced by the drug |
A
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The presence of spare receptors may do all of the following EXCEPT:
A) Affect the Emax (efficiency) in competitive inhibition B) Affect the EC50 (potency) in noncompetitive inhibition C) Make the potency of a drug seem higher than it truly is D) Make a partial agonist seem like a full agonist E) Occur when some factor 'downstream' of receptor binding can limit the responsiveness of the cell |
A
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Define:
ED50 EC50 |
ED50 - the dose of a drug required for 50% of the effect
EC50 - the concentration of a drug required for 50% of the effect (Measures of absolute potency) |
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Name two factors which can cause differences in drug selectivity for different receptors.
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1. Different potency for different receptors
2. Different access to different tissues 3. Different levels of spare receptors (?) |
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Name three ways a drug can antagonize another without affecting the same receptor.
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1. Chemical antagonism (ex. chelators, antibodies like infliximib/remicade[antiTNF-alpha], receptor decoys like etanercept[TNF-R decoy])
2. Pharmacokinetic antagonism (drug reduces absorption or increases clearance of another) 3. Physiologic antagonism (Drug interacts with a body system which antagonizes the effect of the other drug) |
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Which is affected in reversible competitive inhibition?
A) Efficiency B) Potency C) Both |
B
Efficiency is left alone - i.e. effect is surmountable |
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To get the same effect from a drug in the presence of a reversible competitor, how many times must you increase the dose?
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[A']/[A] = 1 + [B]/Kb
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Which is affected in noncompetitive inhibition?
A) Efficiency B) Potency C) Both |
Efficiency
(Potency stays constant unless there are spare receptors, in which case it decreases) |
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Irreversible Competitive inhibition without spare receptors has the most similar effect to:
A) Competitive Inhibition B) Noncompetitive Inhibition without spare receptors C) Noncompetitive Inhibition with spare receptors D) Allosteric modulation |
B; it's the same but permanent
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Competitive inhibitors...
A) Bind the active form of a receptor more than the inactive form B) Bind the inactive form of a receptor more than the active form C) Bind both forms of the receptor equally |
C
The inhibit by blocking the binding site from the agonist. |
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A drug which favors the inactive form of a receptor is called a/an
A) Competitive Inhibitor B) Noncompetitive inhibitor C) Allosteric Modulator D) Inverse agonist |
D
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A dose-effect curve that is very shallow may indicate...
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That a drug binds multiple receptors at different affinities
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Potentiation of a drug may describe
A) A reduced ED50 B) An increased Emax C) Both |
C;
increased potency or efficiency |
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Diazepam is a ____________ of GABAa receptors; Flumazenil is a ____________ for the benzodiazepine binding site.
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Diazepam is a positive allosteric modulator of GABAa receptors; Flumazenil is a competitive inhibitor for the benzodiazepine binding site.
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Name two distributions that are often reported on quantal dose-effect curves.
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Cumulative frequency distribution (ex. total number of deaths) and frequency distribution (ex. deaths in a given dose range)
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What is the ED50 of a quantal dose-effect curve?
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The median dose needed to achieve the effect.
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Besides pharmacokinetic difference within a population (drug absorption, metabolism, clearance), what other major factors can influence a response to a drug?
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Pharmacodynamic variability - number of receptors, distribution of receptors, properties of receptors due to environment/disease/genetics.
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Define the therapeutic index of a drug.
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LD50/ED50
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What is a weakness of the therapeutic index?
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It is not very valuable if the dose-effect curves for effect and lethality are non-parallel.
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Name this value:
100x[(LD1-ED99)/ED99] and explain its usefulness |
Standardized Safety Margin - it takes into account variability in the population. But it is often not reported.
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After taking a drug of one class for a long time, a patient starts taking a second drug of that class, but needs higher doses than most individuals. This is an example of...
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Cross-tolerance
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Tachyphylaxis is best exemplified by which drug:
A) Flumazemil B) Etanercept C) Infliximib D) NO |
D - tachyphylaxis means a very short-lasting effect.
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Which of the following is not a common class of side-effect of a drug:
A) Pharmacologic B) Pharmacodynamic C) Pharmacokinetic D) Allergic/hypersensitivity E) Idiosyncratic |
B
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Is the following an adverse drug reaction?
A very elderly patient has been taking a drug for 5 months and one day she experiences a very strong dizzy spell. She visits her doctor who tells her that dizzy spells can be an occasional side effect of the drug, but keeps her on the same regimen. |
No; an adverse drug reaction must be severe enough to cause a change in the treatment plan.
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For the most part, which class of results consistently show significant improvement under placebo administration?
A) Objective or quantal outcomes B) Subjective outcomes C) Obesity and insomnia D) Pain E) All of the above |
D
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A high standard deviation will make a cumulative frequency distribution ____ shallow.
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A high standard deviation will make a cumulative frequency distribution more shallow.
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