Principles of Pharmacodynamics Flashcards
What is a drug?
a chemical that interacts with the body and causes a specific physiological response
What is a drug target site?
cellular macromolecule that will bind a certain drug
What is a receptor?
drug recognition site, when unbound it is unfunctional/functionally silent
What is an agonist?
binds to a receptor and activates it
What is an antagonist?
binds to receptor but has no activation
What is affinity?
How avidly a drug binds to its receptor
What is efficacy?
The ability of a drug to cause a conformational change within the receptor in order to have its physiological effects
What is potency?
measure of drug strength
What is selectivity?
only binding to a particular subset of receptors, usually requires low dosage
What is a partial agonist?
less efficacy and affinity, cannot cause max tissue response
What are the principle differences between competitive and irreversible antagonists?
competitive = propranolol irreversible = hexamethonium --> increasing level of agonist has no effect on tissue response
Describe the four main categories of drug target sites and give one example of a drug acting at each of these different target sites
RITE
Receptors –> beta receptor agonists eg. adrenaline
Ion channels –> voltage sensitive calcium channels eg. nifedipine
Transport systems –> uptake mechs eg. Na/K+ - digoxin
Enzymes –> anticholinesterases eg. neostigmine or phygostigmine
Specify two classes of drugs that do not act by binding to proteinaceous target sites
antacids –> chemical reaction
diuretics –> ion channels
Define ‘receptor reserve’. What is the importance of this physiological pheonomenon?
repeated activation will exhaust mediator stores –> all receptors endocytosed
maximal response can be achieved without occupying all the receptors
What is the structure activity relationship?
The structure–activity relationship (SAR) is the relationship between the chemical or 3D structure of a molecule and its biological activity.
Differentiate between the four principal types of drug antagonism. Give one example of each type of agonist.
receptor blockade
homeostatic/physiological antagonism - Na+A and H2 - decrease in TPR
chemical - dimercaprol - chelates lead
pharmacokinetics - upregulates liver enzymes eg. Warfarin
Name four main receptor families
Ion channel
G-protein
TK
intracellular/DNA/nuclear eg. steroids
List five cellular mechanisms that may account for drug tolerance
exhaustion of mediator stores receptor endocytosis increased metabolism change in receptors physiological
Which way do competitive antagonists shift the log dose-response curve?
RIGHT
same maximal response achieved
Which way do reversible antagonists shift the log dose-response curve?
LEFT
at high dose, maximal response is impaired
