Chapter 2: Pharmacodynamics Flashcards
A molecule to which a drug binds to bring about a change in function of the biologic system
Receptor
A molecule to which a drug may bind without changing any function
Inert binding molecule or site
Specific region of the receptor molecule to which the drug binds
Receptor site
Receptor that does not bind drug when the drug concentration is sufficient to produce maximal effect; present if Kd > EC50
Spare receptor
Component of a system that accomplishes the biologic effect after the receptor is activated by an agonist; often a channel, transporter, or enzyme molecule, may be part of the receptor molecule
Effector
A drug that activates its receptor upon binding
Agonist
An agonist that activates the same receptor as other drugs in its group but also causes additional downstream effects that are not seen with other agonists in the group
Biased agonist
A drug that binds to the receptor without activating it and thereby prevents activation by an agonist
Pharmacologic antagonist
A pharmacologic antagonist that can be overcome by increasing the concentration of agonist
Competitive antagonist
A pharmacologic antagonist that cannot be overcome by increasing agonist concentration
Irreversible antagonist
A drug that counters the effects of another by binding to a different receptor and causing opposing effects
Physiologic antagonist
A drug that counters the effects of another by binding the agonist drug (not the receptor)
Chemical antagonist
A drug that binds to a receptor molecule without interfering with normal agonist binding but alters the response to the normal agonist
Allosteric agonist, antagonist
A drug that binds to its receptor but produces a smaller effect (Emax) at full dosage than a full agonist
Partial agonist
Activity of a receptor-effector system in the absence of an agonist ligand
Constitutive activity
A drug that binds to the non-active state of receptor molecules and decreases constitutive activity
Inverse agonist
A graph of the increasing response to increasing drug concentration or dose
Graded dose-response curve
A graph of the increasing fraction of a population that shows a specified response at progressively increasing doses
Quantal dose-response curve
In graded dose-response curves, the concentration or dose that causes 50% of the maximal effect or toxicity. In quantal dose-response curves, the concentration or dose that causes a specified response in 50% of the population under study
EC50, ED50, TD50, etc
The concentration of drug that binds 50% of the receptors in the system
Kd
The largest effect that can be achieved with a particular drug, regardless of dose, Emax
Efficacy, maximal efficacy
The amount or concentration of drug required to produce a specified effect, usually EC50 or ED50
Potency
_____ is a drug capable of fully activating the effector system when it binds to the receptors.
- Has high affinity for the activated receptor conformation, and sufficiently high concentrations result in all the receptors achieving the activated state (Ra – Da)
Full agonist
A _____ produces less than the full effect, even when it has saturated the receptors (Ra–Dpa + Ri–Dpa), presumably by combining with both receptor conformations, but favoring the active state.
In the presence of a full agonist, this acts as an inhibitor.
Partial agonist
Types of transmembrane signaling receptors:
_____ are the most common type of receptors in the body.
GPCRs
Types of transmembrane signaling receptors:
_____ bind to the extracellular domain of molecules that incor- porate tyrosine kinase enzyme activity in their intracellular domains
- Insulin, epidermal growth factor
Membrane-spanning receptor- effector enzymes
Frequent or continuous exposure to agonists often results in short-term diminution of the response, sometimes called _____
Tachyphylaxis
