Drug-Receptor Interactions Flashcards
Define: Affinity
strength of the physical interaction between a drug and receptor, how tightly is the drug bound to the receptor?
Define: Specificity
how selective a drug binding to one type of a receptors but not others
Define: Efficacy
how effective a drug is at eliciting a receptor response
Define: Potency
how much of the drug is needed to produce an effect
Describe: Radioligand Binding Assay
- drug is radioactively tagged
- radioactive ligand is placed in a vessel with receptor
- the solution is filtered- ligand-receptor complex will remain whereas unbound ligand can be washed away
- bound ligands will produce a light that can physically measure the chemical interaction between the drug-receptor complex
Define: Receptor Fractional Occupancy
(receptor bound with drug)/ (free receptor + receptor bound with drug)
What information can be found on a drug binding curve?
Kd = drug concentration when 50% of receptors bound with the drug (affinity= 1/Kd: lower the Kd, higher the affinity)
Define: Kd
drug concentration when 50% of receptors bound with the drug, is used to measure affinity
What information can be found on a dose response curve?
-EC50= the concentration of a drug that produces 50% of maximal response (potency: lower the EC50, higher the potency)
-maximum response= reflected by the upper limit of the curve (efficacy: higher the maximum line, higher the efficacy)
What factors affect a drug’s clinical effectiveness?
-potency
-efficacy
-the ability to reach its receptors
Define: Agonist
ligand that binds to a receptor and activates its signaling, shifting the equilibrium towards he active site
Define: Antagonist
ligand that binds to a receptor, but does not activate signaling- does not effect the equilibrium between active and inactive state, but prevents agonist binding
Define: Inverse Agonist
ligand that produces the opposite effect of the agonist, shifting the equilibrium towards the inactive state
Define: Partial Agonist
ligand that produces a lower response than an agonist, shifting the equilibrium slightly towards the active state
Describe: Chantix (varenicline)
nicotinic ACh receptor partial agonist that replaces nicotine (a full agonist) for smoking cessation
Describe: Narcan (naloxone)
opioid receptor antagonist that has a high affinity for the receptor that treats opioid overdose with little or no symptoms by itself. IM or intranasal spray that is effective 2-5 minutes after administration
Define: Competitive Antagonist
competes with the agonist for binding of the same site as agonist
How does an agonist + competitive antagonist effect a dose binding curve?
maximal response does not change, but EC50 is increased- a sufficient amount of agonist can overcome a given concentration of competitive antagonist
Define: Noncompetitive Antagonist
receptors can have multiple binding sites (allosteric site) so the antagonist binds to a seperate site and interferes with agonist binding or modifies receptor activity
How does an agonist + noncompetitive antagonist effect the dose binding curve?
maximal response is reduced, but EC50 may or may not be changed- no amount of agonist can effect the results induced from noncompetitive antagonist
Describe: Lock and Key Model
the ligand and receptor are complementary to each other
Describe: Induced Fit Model
“hand and glove” model, there are conformational changes of the ligand and the receptor
Describe: Conformational-Selection Model
protein receptor fluctuates among several conformational states and only some of the conformations states allow ligand binding
What are drug targets mentioned in lecture?
proteins(receptors, enzymes, binding sites on ion channels) and DNA
