Tachyphylaxis
rapid decrease in response to a drug after repeated doses over a short period of time
Potency
a measure of the amount of drug necessary to produce an effect of a given
magnitude.
EC50
Concentration of the drug that produces 50% of maximal effect
Efficacy
the ability of a drug to elicit a response when it interacts with a receptor.
Emax
maximal response or effect, the biggest effect a drug can produce; assumes all receptors are occupied by the drug and no increase in
response will be observed if more drugs are added; only holds true if there are no "spare" receptors present
affinity
the strength of the attraction (interaction or binding)
between a ligand (drug) and its receptor.
intrinsic activity
ability of a drug to activate a receptor upon binding
inverse agonist
exert the opposite pharmacological effect of a receptor agonist
Quantal response
the magnitude of the dose on the proportion of a
population that responds.
ED50
the drug dose required to produce a defined therapeutic or
desired response in half of the population
Therapeutic Index (TI)
ratio of the dose that produces toxicity to the
dose that produces a clinically desired or effective response
TD50 / ED50