Ligand Receptor Interactions

property of a drug that determines drug’s ability to activate a receptor and produce a response (contributes to Emax)

intrinsic Activity

drug that stabilizes the receptor in its active state and produces a maximal response equivalent to the endogenous ligand; drugs that reach Emax 100%

Full Agonist

drug with intrinsic activity >0 but <1 that cannot produce the full Emax of the natural ligand even at full receptor occupancy; may reduce (inhibit) the effect of a full agonist when both are present 

Partial Agonist

a ligand that stabilizes the inactive receptor state and reduces constitutive (basal) receptor activity, producing effects opposite to an agonist 

Inverse Agonist

reversible antagonist that binds that same site as the natural ligand, prevent agonist binding; it reduces potency (shifts dose-response right) but does not reduce Emax and can be overcome by increasing agonist concentration 

Competitive Antagonist

any antagonist that does not reversibly act at the agonist binding site (cannot be outcompeted); typically reduces efficacy (reduces Emax) and cannot by overcome by increasing agonist concentration

Non-competitive Antagonist

an antagonist that binds a site distinct from the agonist (——) site; it is non-competitive, reduces Emax without changing EC50, and cannot be overcome by more agonist (some _____ ligand can instead be activators) 

Allosteric Antagonist

an antagonist that covalently binds the receptor (cannot be released), making it non-competitive; it decreases efficacy (Emax) and cannot be outcompeted by higher agonist concentrations  

Irreversible Antagonist

substance that neutralizes or inactivates another drug/ligand by direct chemical interaction (non-receptor mechanism); an antacid neutralizing HC is ex.

Chemical Antagonist

drug that oppose effect of another by acting at a different receptor or pathway (producing counteracting physiological effect)

Physiological Antagonist