2 Pharmacodynamics Flashcards
Pharmacodynamics
what the med does to the body
Cellular Level
- where drugs exert primary action
- where receptors are (on or within cell)
- # of receptors is finite - can change
Down Regulation
Body pulls out receptors
-ex.) too much stimulus, ephedrine
Up Regulation
Body creates more receptors
-ex.) beta-blocker - cannot abruptly stop!
When do receptor mediated responses plateau?
When receptors are saturated
Affinity
strength of binding between drug and receptor
-stronger affinity can kick off lesser
Dissociation Constant (Kp)
measure of a drugs affinity for a give receptor. The concentration of drug required in solution to achieve 50% occupancy of its receptors
Agonist
drug which alters physiology of cell by binding to plasma membrane or intracellular receptor
- increases natural activity
- ex.) epi, alpha agonist
Strong Agonist
causes maximal effects even though it may only occupy a small fraction of receptors
Weak Agonist
must be bound to many more receptors than a strong agonist to have same effect
Partial Agonist
fails to produce effects, even if all receptors are occupied
Inverse Agonist
Not an antagonist. Binds to receptor site and causes opposite effect of agonist
- forces negative effect
ex. ) H2 “antagonist”
Antagonist
Inhibits or blocks action caused by agonist
Competitive Antagonist
competes with agonist for receptors
ex. ) reversal agents
- can be overcome by high doses of agonist –> surmountable
Noncompetitive Antagonist
can still block agonist, just through different site
- induces conformational change in receptor
- insurmountable - even high doses of agonist cannot overcome antagonism
Irreversible Antagonism
Agent competes with agonists for agonist binding receptor and combine PERMANENTLY