Pharmacodynamics Flashcards
What is a receptor?
A macromolecule whos biological function changes when a drug binds to it
Many drugs bind to receptors but do not cause change, competitive inhibi
What is affininty?
Measure of the propensity of a drug to bind receptor.
What is are the events that get triggered from receptor binding called?
Signal transduction
What are the types of bonds between drug and receptor?
Van Der Waals
Ionic
Covalent Interactions
Mulitple Bonds and Interactions are used
What happens if we put two drugs acting at same receptor?
They will compete for transient binding of the receptor.
Higher concentration drug has greater chance of binding.
Know this Slide
How do we measure or quantify a drug receptor interaction?
Dose - Response Curve
What is the EC50 Value?
Concentration/Dose of a drug that produces %50 max response.
What are features of a Log dose - response graph?
- Sigmoid/Linear Curve
- Compressed Dose Scale
- Proportionate doses at equal intervals
- Straightens line
- Easier to analyze
What is Emax and what does it measure?
Maximal effect from a drug. It measures efficacy of a drug
Efficacy is ability of bound drug to change receptor to make an effect.
Some bind receptors but do not produce effect.
What does the Kd Value mean?
Concentration of a drug that occupies 50% of the total number of receptors at equilibirum.
Why is the Kd50 Value different from the EC50
There are more receptors in the body than needed to produce maximal response. Do not need to activate 50% of receptors to achieve 50% maximal response.
What is an agonist?
Drug which binds to the receptor and produces an effect.
What is a partial agnostic?
Has an affinity for a receptor but lower efficacy and lower Emax than a full agonist.
What is an antagonist?
a drug which binds to receptor but has no efficacy(produces no effect) but competes for binding against other ligands.
2 Types: Competitive (reversible)
Noncompetitive (irreversible)
Why is a partial agonist useful?
partial agonist acts as an antagonsit in the presence of a full agonist. Blocks full effect
What are 2 clinical examples of a partial agonist being useful?
Example: Buphrenorphine as an opioid analgesic instead of morphine. (Less likely overdose, lower level of dependance, lower risk of abusing it)
Example: Pindolol for High Blood Pressure and Abnormal heart Rythms. Noraepinephrine(Full Agnonist) from overactive sympathic nervous system. Partial Agonist Pindolol competitevly binds reducing effects.
B1 Andregenic Receptors
Can the usual effect of an agonist be achieved if in the presence of a reversible competitive antagonist?
Yes, if the dose of Agonist is increased
Achieve a Rightward shift of Dose - Response Graph
Can a higher dose of agonist achieve maximal effect in the presence of a non competitive irreversible antagonist?
NO
What happens to the Emax of an agonist in the presence of a non competitive antagonist?
E max Depresses cannot reach maximum effect.
If dose of antagonist keeps increasing - Can get E max to 0
What is an inverse agonist?
Some receptors have intrinsic activity when nothing is bound, when ligand binds the activity is reduced.
What is it called when ligand B binding potentiates the response of agonist A.
Allosteric Interaction
Explain the Allosteric effects on GABA.
Benzodiazepine drugs potentiate the response to gama aminobutyric acid(GABA) when they bind to the GABAA.
GABA involved in Inhibition Sedation - it is a neurotransmitter
When GABA binding is effected it causes chloride channels to open for longer.
Remember this
Clinical Revelance of Different types of Antagonism?
Easier to treat overdose and poisonous by a competitive reversible system.
Harder to treat with irreversible system.
What does a quantal dose curve mean?
indicates sensitivity of a given population to a drug.
What is frequency distribution?
Each bar shows number of people responding to that specific dose.
What is Cumulative Frequency?
Each bar shows the number of people responding to that dose and all the lower ones.
What is the TD 50
Concentration that is toxic to 50% of the population.
What is the ED 50
Concentration of the drug that 50% of the population respond to,
What is the LD 50
Lethal Dose in 50% of the population.
What is the Therapeutic Window
It is the difference between the minimum effective doses for a desired response and an adverse response.
What are the 4 types of signal transduction mechanisms?
G- Protein coupled receptor system - Half of all drugs work through this.
Ion channel Receptors
Enzyme as receptors
Nuclear Receptors - For Hormones and Lipid Soluble Drugs - Bind in cytosol.
2,1,3,4 In order Fastest to Slowest
