Flashcards in Session 8 Deck (43)
How do all drugs exert their effects?
By binding to a target, majority are proteins.
Do drugs bind reversibly or irreversibly?
Reversibly with receptors.
What governs drug binding?
Association and dissociation rates.
What is the importance of concentration of drug molecules?
Concentration around the receptor is critical in determining drug action.
Drugs with equivalent molar concentrations have the same concentration of drug molecules.
Drugs with equivalent concentrations by weight may not.
What is the equation for grams per litre?
Molecular weight x Molarity
What is affinity?
The likelihood of a ligand binding to its target
What is efficacy?
Likelihood of activation.
Do Antagonists have affinity or efficacy?
Do Agonists have affinity or efficacy?
How can binding information be found out?
By the binding of a radioligand.
What is Bmax?
The maximum binding capacity
What can the Bmax tell you?
The number of receptors
What is Kd?
The dissociation constant and concentration needed for 50% occupancy
What can you measure with the dissociation constant?
What does a low Kd value relate to?
A higher affinity.
When are concentration response curves used?
Measuring a response in cells/tissues.
When are dose response curves used?
When measuring a response in a whole animal.
What is Emax?
The maximum response.
What is EC50?
The effective concentration giving 50% of the maximal response.
It can be used to measure Potency
What is Potency?
Extra point - What governs it?
A combination of affinity and efficacy.
Extra point - The number of receptors.
If an agonist has the same Emax value, will the efficacy be the same? What id the efficacys were different?
Not necessarily. If the efficacys are different then the Emax value will be different.
What is the goal of treatment in asthma?
To activate Beta 2 adrenoceptors to relax the airways.
What is Salbutamol?
A beta 2 adrenoagonist. It is high affinity and Beta 2 selective efficacy. It has side effects and limits Beta 1 activation.
What is Salmeterol?
A longer acting Beta 2 adrenoagonist.No selective efficacy and prevents Beta 1 activation and side effects through difference in affinity only.
When can less than 100% receptor occupancy give 100% response?
When EC50 is smaller than Kd = 50% of the maximal response needs less than 50% of the receptor occupancy.
What effects the relationship between receptor occupancy and response?
It is non linear response and influenced by both transduction system and amplification (produced by second messengers) and properties of the tissue.
How do spare receptors increase the response of a cell?
They increase sensitivity and allow responses at low concentrations of agonists.
What does number of receptors have an effect on?
What are partial agonists?
An agonist that cannot produce a maximal effect even with full receptor occupancy.