PHARM A20/21: Drug Receptor Mechanisms Flashcards
What is the difference between selective and non selective ion channels?
Selective ion channels will only allow a specific ion to pass through following activation, while non-specific channels are less strict about what passes through
What is Ka and Kd in the context of drug receptor reactions?
Ka is the association rat constant- the rate at which a ligand will bind the receptor; Kd= dissociation constant- rate at which a ligand will dissociate from the receptor
What is the difference between affinity, efficacy, and potency? Which is most important in designing a drug?
Affinity is the chemical forces that cause a drug to associate with the receptor (how tightly it binds); Efficacy- how much effect the drug has on the receptor; Potency is the dose of drug necessary to produce a specified effect; Efficacy most important characteristic
What factors are determinants of the response to a given drug?
Intrinsic efficacy and the number of receptors in target tissue
What are spare receptors?
Receptors present that exceed the number necessary to produce a maximal response in a target tissue
What is the difference between an orthosteric and allosteric drug?
Orthosteric drugs bind to the active site of a receptor, while allosteric molecules bind to a different site that changes the activity of the receptor
What is an antagonist?
A drug that binds to a receptor but does not elicit a cellular response; prevent agonists from producing a response
True or False: Antagonists alter the active state: inactive state equilibrium.
False
What is an inverse agonist? How does it work?
A drug that binds to a receptor to produce an effect opposite that of an agonist- it stabilizes receptors in the inactive state and so there will be no spontaneous activity
What is the threshold?
The dose that produces a just-noticeable effect
What is ED50? The EC50%?
The dose that produces a 50% of maximum response; The blood concentration that produces 50% of maximal response
What is the ceiling (ED99)?
Lowest dose that produces 50% of maximum response
True or False: Partial agonists have both agonist and antagonist properties.
True
How can the relative potency of two drugs be calculated?
Relative potency= ED50 drug B/ ED50 drug A
What are physiologic antagonists?
Drugs that work through different mechanisms to produce opposing physiologic responses.
What is competitive antagonist Inhibition?
Increasing doses of antagonist with a fixed dose of agonist
What is the IC50/ ID50?
IC50 is the concentration in dose of the antagonist that produces a 50% decrease in the effect of the agonist
What is a quantal dose-response curve?
Used when the dose of a group to produce a specified effect in a single patient is measured
What are the two different types of Quantal-Dose Response Curves and what do they measure?
1) Quantal dose response curves plot dose on the x axis and % responders on the Y axis 2) Cumulative Quantal Dose- Response Curve plots the cumulative response off all doses up to a particular level
How can the safety index be measured? What is the range required by the FDA?
Safety Index= LD1 (lethal dose for 1%) / ED99 (effective dose for 99%); FDA want index of greater than 10
How is the therapeutic index calculated?
LD50/ED50
What are Biologic Response Modifiers (aka Biologics)?
Wide range of biologic products ranging from vaccines, blood and blood components, gene therapy, recombinant proteins
What value of safety index indicates that the drug is not safe?
What are the two major types of Drug-Drug interactions?
Pharmacodynamic interactions and pharmacokinetic interactions
What describes the nature of the interaction between caffeine and acetominophen?
Potentiation
What are the types of pharmacokinetic interactions?
Interactions affecting absorption, distribution, metabolism, and excretion.
