MMT: Pharmacodynamics Flashcards
efficacy: what it means, where to find it on a dose-response curve
efficacy: the ability of a drug to cause a response; agonists have it, antagonists do not. it is found on the vertical axis
potency: what it is and where to find it on a dose-reponse curve
the molar concentration of a drug required to produce a response. it is found on the horizontal axis.
what is the Ed50 value? what does it measure?
dose of drug required to produce a half maximal response, and thus measures potency; a lower Ed50 = higher potency
Explain Occupancy Theory and be able to use this theory to explain the mechanism of action of different kinds of drugs, including the characteristics of dose response data on producing effects.
occupancy theory: tissue response is a linear function of receptor occupancy by a drug; drugs combine with receptors at a rate dependent on concentrations of receptor and drug, as well as affinity of the drug for the receptor.
Define the terms agonist and antagonist and be able to explain the mechanism of action of different drugs that fall into these two broad classes (i.e., full agonists, partial agonists, neutral antagonists, inverse agonists, and competitive, noncompetitive, chemical and physiological antagonists).
antagonist: bind to the receptors but to not elicit a biological response. they have affinity but low efficacy.
what are the two main types of antagonists? describe their actions and how they impact the dose-response curve
competitive: binds to the same receptor as the agonist. causes a rightward shift in a dose response curve with no change in maximal effect.
noncompetitive: bind to a site separate than the agonist and decrease the ability of the agonist-occupied receptor to genrate a response. in a dose-response curve, we see an overall decrease in max response.
increasing amounts of antagonist will further decrease the max response
what is a negative allosteric modulator?
a type of noncompetitive antagonist. they have affinity for the receptor but not for the same site as the agonist. they can bind the receptor and change its conformation, typically rendering the receptor non-functional.
what is an irreversible antagonist?
an antagonist that binds to the binding site of a receptor and reacts with functional groups at the binding site, blocking interaction with the agonist permanently. it reduces overall active receptors, and with enough antagonist the receptor can become completely blind to agonist.
why do irreversible antagonsits have no Kd
they have no off-rate!
what is a chemical antagonist?
a compound that can bind to or inactivate an agonist before it can bind to a receptor.
what is a physiological antagonist?
the inhibitor may not be at the same site as the drug it is inhibiting. ex: muscarininc receptor agonists raise HR, beta-adrenergic receptor agonsists lower HR. their actions antagonize each other but not via the same receptors.
what is a partial agonist?
even saturating amounts of drug fail to elicit a full response
what is Kd?
concentration of drug required to occupy 50% of receptors; lower Kd = higher affinity
