Pharmacodynamics (session 6) Flashcards
How do drugs exert an effect?
By binding to a target
True or false: the concentration of drug molecules around receptors is critical in determining drug action
TRUE
True or false: most drugs bind irreversibly to receptors
FALSE - reversibly
What does a ligand need in order to bind to a receptor?
Affinity for the receptor
What is the ability to generate a response called?
Efficacy
What is intrinsic efficacy?
The ability to switch a receptor on
What is the difference between agonists and antagonists?
Agonists have intrinsic efficacy and efficacy
Antagonists have affinity only (no efficacy or intrinsic efficacy)
How do we measure drug-receptor interactions by binding?
By binding of a radioactively labelled ligand (radioligand) to cells or membranes prepared from cells (many cells/many receptors)
What is Bmax?
Maximum binding capacity (info about receptor number)
What is Kd?
Dissociation constant-index of affinity, tells you about the strength of the interaction. Concentration of ligand required to occupy 50% of the available receptors
What does a low value of Kd mean?
High affinity
What is EC50?
Effective concentration giving 50% of the maximal response - measure of agonist potency
What does EC50 depend on?
Affinity and intrinsic efficacy and cell/tissue-dependent factors such as the number of receptors
What effect do beta2-adrenoceptors have on asthma?
Relaxation of airways
Why is it hard to design a drug that only targets beta2-adrenoceptors?
The binding site for beta1 and beta2 are very similar