1.11 Pharmacodynamics II Flashcards
Define the term Kd and its relevance to affinity
Kd = dissociation constant
- It’s the amount of drug it takes to bind 50% of receptors
Smaller amount of Kd = higher attraction (affinity)
Describe the role of drug dose in response
They are dose-dependent
EC50 = concentration of drug to cause 50% of max effect
- Think about potency
Differentiate between graded and quantal dose-response curves
Graded response - plots the drug effect vs. concentration
- Uses EC50
Quantal dose-response curve - plots rate of outcome of drug vs. drug concentration
- Uses ED50, TD50, and LD50
What are the 2 antagonist classifications
Receptor antagonists
- Active site binding
- Allosteric binding
Nonreceptor antagonists
Define intrinsic activity and its relationship to efficacy, antagonists, and partial and full agonists
Intrinsic activity - maximal effect of a drug
Intrinsic activity = efficacy
Full agonists have an intrinsic activity of 1
Partial agonists have intrinsic activity less than 1 and greater than 0
Pure antagonists = no intrinsic activity
Define an inverse agonist
Opposite effect of agonist
Describe the effects of spare receptors on Kd and EC50
It can reach max effect, even if all receptors aren’t bound
Describe the effect of high and low doses of noncompetitive antagonists on the dose-response curve in the presence of spare receptors
High dose of noncompetitive agonist wipes out the needed receptors and there’s a partial agonist with low potency
Low dose has max effect and full agonist
Define therapeutic index and its relevance to pharmacotherapy
TI = (TD50)/(ED50) = (Toxic Dose 50)/(Effective dose 50)
The higher the TI, the wider the TW, the safer the drug
Most drugs bind via what interactions?
Van der waals
Define affinity
Attractiveness of a drug for its receptor
The effects of drugs are ___ ___
Dose-dependent
ED50
Therapeutic Effect
- Concentration of drug needed to produce a therapeutic effect of 50% of population
TD50
Toxic effect
LD50
Concentration of drug you see death in 50% of patients
What does R* mean?
It is a constitutivelly active
- Drug doesn’t have to be bound to receptor and the receptor is still bound
D+R is what type of response
Agonist
Within active cite binding in antagonists, it can be reversible and irreversible, describe them.
Reversible = competitive antagonist
- Agonist and antagonist compete at active site of receptor
Irreversible = noncompetitive active site antagonist
- agonist and antagonist are bound at the same time because of covalent bond
Within allosteric binding in antagonists, it can be reversible and irreversible, describe them.
Reversible and irreversible = noncompetitive allosteric antagonist
- Agonist only binds to the active site
Describe nonreceptor antagonists
Chemical antagonist
- Antagonizes (works against) the situation
- Binds nothing
Physiological antagonist
- The physiologies are antagonists
- Don’t work together b/c receptors and signals work against each other
Define potency
Reponse of a drug over a given range of concentrations
Higher EC50 = decreased potency
Describe the different types of antagonists
Competitive
- Shifts graph to right
- EC50 gets higher
- Add more drug to block antagonist
Noncompetitive
- Irreversible antagonist
- EC50 doesn’t change
- Max effect changes
- Efficacy changes
Define therapeutic window
You have an effect to a drug, but no toxicity or lethality
