Pharmacodynamics 2 Flashcards
E-max
Efficacy or the maximal response to drug
Potency
Concentration of the drug at which 50% of the maximal response is observed
Partial agonist
Elicits a portion of the complete effect, may be more potent than the full agonist, however. Mechanism not fully understood, but probably doesn’t completely elicit conformational changes
Antagonist
Binds receptor, but no response is seen when antagonist is applied independentaly
Physiological antagonist
Works at an independent site from agonist, but has opposing effects
Chemical antagonist
Combination of agonist and antagonist, with resulting inactivation of the agonist
Competitive antagonism
Binds reversibly to the active site, inhibiting the action of the agonist. Shifts log curve right, or EC50 shift to a decrease in potency
Noncompetitive antagonism
Binds active or allosteric site irreversibly, no effect on EC50, decrease in efficacy. Shift down on dose response curve
Inverse agonist
Decreases constitutive activity of the receptor activity, antagonist keeps activity at constitutive levels if applied with inverse agonist
Mechanism of spare receptors
Don’t need 100% of receptors to be filled to get 100% of the response. 1) receptor remains activation after agonist departs. 2) Cell signalling pathways allow significant amplification
Quantal dose response curves
All or nothing response, frequency distribution of responders plotted versus the log dose
Therapeutic index
Lethal dose 50 / Effective dose 50, larger the TI - the safer the drug
Certainty safety factor
Ratio between the concentration of drug that is toxic to 1% of the population vs. the dose that is therapeutic for 99% TD1/ED99, greater the ratio, less toxic the drug
Tolerance and tachyphylaxis
Efficacy may change (read decrease) during therapy, if it happens rapidly this is tachyphylaxis.
