2. Affinity and Efficacy Flashcards
agonist’s AFFINITY is the ability..
to BIND to RECEPTORS
EFFICACY is the ability to..
Produce a RESPONSE
what are FULL AGONISTS
drugs whose MAXIMUM RESPONSE is the LARGEST a tissue/cell is capable of giving
- reaches 100% RESPONSE
- have HIGH EFFICACY
what are PARTIAL AGONISTS
drugs whose MAXIMUM RESPONSE is LOWER than full (even when occupy all available receptors)
- DO NOT reach 100% response
- Lower efficacy
what makes a drug more POTENT
LOWER EC50 (conc. when response is 50%)
- more Left on curve
how are ANTAGONIST’S AFFINITY and EFFICACY
HIGH AFFINITY but NO EFFICACY
what happens to the LOG-CONC RESPONSE CURVE for an AGONIST with INCREASING ANTAGONIST CONCS
SHIFT to RIGHT
how is the RIGHT SHIFT for AGONISTS with COMPETITIVE ANTAGONISTS
PARALLEL
(higher EC50)
how can a COMPETITIVE ANTAGONIST be DISPLACED/REMOVED
by INCREASING CONC. of the AGONIST
WEAK CHEMICAL BOND between drug and receptor means AGONISTS BIND..
REVERSIBLY
COMPETITIVE ANTAGONIST for ACETYLCHOLINE and what does it do
ANTROPINE
- BINDS to MUSCARINIC RECEPTORS at ach binding site thus BLOCKS ACH BINDING
causes a RIGHT, PARALLLEL SHIFT of the RESPONSE CURVE
PROPIVERINE is a NON-COMPETITIVE ANTAGONIST of ACH at MUSCARINIC RECEPTORS. how does it work
BINDS to ANOTHER SITE
to PREENT the EFFECTS Of STIMULATION of the muscarinic receptor by ACH
how is the RESPONSE CURVE for ACH WITH NON-COMPETITIVE ANTAGONIST (propiverine)
like the curve for partial agonist (smaller)
RIGHT SHIFT (HIGHER EC50 and LOWER POTENCY)
& LOWER MAXIMUM ACTIVITY (doesn’t reach 100% response) - LOWER EFFICACY
- NOT PARALLEL
how is the MAXIMAL RESPONSE for a COMPETITIVE ANTAGONIST
SAME, shifted right in a PARALLEL manner
how is the MAXIMAL RESPONSE for a NON-COMPETITIVE ANTAGONIST
REDUCED maximal response (shorter curve)
and the curve is NOT PARALLEL
what are IRREVERSIBLE ANTAGONISTS
and how are they displaced
BIND IRREVERSIBLY to the receptor (either at binding site or another site)
due to COVALENT INTERACTION
therefore you CANNOT DISPLACE IRREVERSIBLE ANTAGONIST
(even with high concs of agonist, agonist can only bind again if the cell makes NEW receptor molecules)
- LONGER EFFECT
eg, Haloalkylamines (nitrogen mustards) bind muscarinic receptors,
Novichok (binds acetylcholinesterase)
Propylbenzilylcholine mustard (muscarinic)
MORPHINE agonist
partial agonist:
competitive antagonist:
non-competitive antagonist:
irreversible antagonist:
partial agonist: Buprenorphine
competitive antagonist: Naloxone
non-competitive antagonist: Propiverine
irreversible antagonist: Omeprazole
