Mechanisms of drug action Flashcards
What are 4 types of drug antagonism?
1) Receptor blockade 2) Physiological antagonism 3) Chemical antagonism 4) Pharmacokinetic antagonism
What are 2 types of receptor blockade?
competitive and reversible
Define use dependency
tissue activity required for drug to act. e.g. LAs need to enter tissue via ion channels.
How does physiological antagonism work? example.
Different receptors –> opposite effects in the same tissue. e.g. NA and histamine on B.P.
How does chemical antagonism work? example.
Interaction in solution. e.g. dimercaprol forming complexes with heavy metals after heavy metal poisoning.
How does pharmacokinetic antagonism work? example.
Antagonist –> reduced conc. of active drug at action site Reduced absorption, increased metabolism and increased excretion. e.g. barbiturates.
Define drug tolerance. example.
Gradual reduction in responsiveness to drug with repeated administration. e.g. benzodiazepines.
How can pharmacokinetic factors cause drug tolerance? Examples.
Increased drug metabolism. Barbiturates; alcohol.
What is the relevance of receptor loss on continued exposure to drug?
Increased drug tolerance. Reduced drug effect due to membrane endocytosis. (receptor down regulation)
Define up-regulation of receptors
denervation supersensitivity. Increase in receptor number.
How does receptor change affect drug tolerance? Example.
Drug tolerance increases. Receptor desensitization (conformational change). e.g. nAChR at NMJ on continued exposure.
Give 5 causes of drug tolerance.
- pharmacokinetic factors 2. loss of receptors. 3. change in receptors 4. exhaustion of mediator stores 5. physiological adaption.
Give an example of tolerance caused by mediator store exhaustion.
Amphetamine continued exposure. Running out of endogenous stores of NA.
Outline physiological adaption leading to drug tolerance.
Homeostatic response compensate for changes. Tolerance of drug side effects.
Outline the 4 types of receptor families.
- Ion channel-linked receptors. 2. G-protein-coupled receptors. 3. Kinase-linked type 4. intracellular steroid type receptors.
Diagram showing gross action for each receptor type.
Diagram outlining different receptor type binding sites.
outline of G protein aciton.
