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Drug-receptor Interactions - Coggle Diagram
Drug-receptor Interactions
Affinity & Dissociation Constant
Affinity
likelihood of binding
Dissociation Constant (Kd)
Conc at which
50% of receptors are bound
📉 Kd =📈affinity 📈 Kd = 📉 affinity
Full vs Partial Agonists
Full
Produces
max
possible response
e.g. Phenylephrine
Partial
Can't produce a full response
even at 100% receptor occupancy
e.g. Clonidine
Binding ≠ activation
Agonist
Binds +
activates
Have
efficacy
Antagonist
Binds,
no activation
Efficacy = 0
Efficacy
Ability to activate once bound
Conc-Effect Curves 📈
Used to study agonist effects
Plateau = all receptors occupied
Effect
does not necessarily equal
receptor occupancy
Physiological feedback loops (e.g. baroreceptor reflex) can reduce measurable response ➰
Potency & EC50
EC50
Conc that produced
50% of max effect
Potency
How much of a drug is needed to produce a given effect
⬇️ EC50 = ⬆️ potency
Depends on:
Affinity Efficacy
Antagonists
Competitive
Bind at
same site
as agonist
Can be
overcome by ⬆️ agonist
Dose-response curve shifts
right
👉
No change
in: max response slope
Non-competitive
Bind at
different site
Prevent receptor activation ❌
Cannot be overcome by more agonist
⬇️:
max response
slope
Schild Plot
Confirms competitive antagonism
Steps
Calculate
Dose Ratio (DR)
= EC50 (with antagonist)/ EC50 (control)
Plot: y-axis = log(DR-1), x-axis = log[antagonist]
Slope = 1
--> confirms competitive antagonist
Allosteric Modulators
Bind to
separate site
from the endogenous agonist
They can:
Change receptor
shape
Alter agonist
affinity
Alter agonist
efficacy
Example:
Benzodiazepines
enhance GABA effects at the
GABA-A receptor