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