Agonists and Antagonists
Potency
A measure of the ability of a drug to produce an effect based on its concentration, influences by drug-receptor affinity
Efficacy
Inherent property that determines its ability to produce its biological effect
What is the intensity of a drug's effect proportional to?
number of drug-receptor interactions
Chemical antagonist
any drugs that binds directly to an agonist and deactivates the agonist by forming a chemical complex, reduces the concentration of agonist, does not depend on interaction with the agonist receptor
Non-competitive antagonists
binds to a site on a receptor other than the agonist binding site and reduces the binding of the agonist or binds irreversibly (covalent bonds) to the same site as the agonist, lower the maximum effect of the agonist
What can excess agonist relative to non-competitive antagonist do?
cannot overcome the blocking effects of the antagonist
What do higher concentrations of agonists relative to competitive antagonists do?
overcome the blocking effects of antagonists
Affinity
tenacity with which a drug binds to its receptor
What can concentration-response curves show?
comparison of relative potencies, determination of antagonist activity, determination of safety, determination of therapeutic index (how effective the drug is)
Competitive antagonist
competes with the binding of agonists at the binding site, binds reversibly, does not alter maximal agonist effect
Main types of antagonists
competitive antagonists, non-competitive antagonists, functional antagonists, chemical antagonists
What does a higher concentration of competitive antagonist relative to agonist do?
displaces or prevents agonist binding to receptor
Functional (physiological) antagonist
has an opposite effect of the agonist but through completely different pathway by binding with different receptors
Do agonists or antagonists have intrinsic activity?
Agonists
What does increase affinity mean?
Less drug needed for a given effect
Full agonist
a drug fully capable of activating the effector system when it binds the receptor- produces 100% effect
Partial agonist
a drug that produces a less than full effect despite receptor saturation- even if all receptors are utilized there will never be a 100% effect
What is potency influenced by?
affinity of the receptor for the drug, number of available receptors
Inverse agonist
drug that binds the receptor but produces the opposite pharmacological effect
Agonists
drugs that bind and activate receptors
Antagonists
drugs that bind to receptors without activating them and consequently prevent the binding of other agonists
Types of agonists
full agonist, partial agonist, inverse agonist
The drug that can produce an effect at ____ drug concentrations is "more potent"
lower