Agonists and Antagonists – Flashcards

Any drug/chemical molecule that binds a receptor and produces an effect -The magnitude of the drug effect is proportional to the amount of drug:receptor complexes formed.

Any drug/chemical molecule that blocks the effect of an agonist

Maximal effect of the drug This is an indicator of efficacy

Drug dose or concentration that produces 50% of the maximal effect

Indication of the amount of drug needed to produce a given effect Defined by the EC50 of the drug The smaller the EC50, the greater the potency

drug concentration required to bind 50% of the receptor sites in the system

Measure of the ability of the drug to bind its receptor site Drugs with a higher affinity are usually more potent. The smaller the Kd, the greater the affinity

Full agonists Partial agonists Inverse agonists

-Increasing concentrations of inverse agonist alone produces an effect. -Increasing concentrations of antagonist produces an effect only in the presence of an agonist.

Competitive antagonist shifts the agonist dose-response curve to the right, increasing EC50 (agonist appears less potent)

They act like antagonists, reducing the Emax (efficacy) of the agonist by reducing the number of available receptors

Reduce Emax by reducing available receptors

Two modes of action 1. prevents binding (lowers affinity) 2. Abolishes activation of the receptor even after the agonist is bound

Have no direct activity on their own Alter the affinity of the agonist for the receptor or the level of receptor activation after agonist binding

when ligands bind to two separate receptors, they produce opposing physiological effects

Interact directly with the drug/agonist - Remove the drug from the system -Prevent the drug from binding to its receptor

A graph of increasing response to increasing drug concentration or dose

A graph of the fraction of a population that shows a specified response at progressively increasing doses