0401 Pharmacodynamics Flashcards
• Dose-response curves • Potency • Efficacy • Drug-target binding • Antagonism • Quantal plots • Hysteresis loops
What are the primary targets of clinical drugs?
Most clinical drugs act on protein targets. Examples of protein targets include enzymes, carriers, channels and receptors.
What is the definition of potency in regards to drugs
Potency refers to the concentration of a drug when the effect of the drug is 50% of it’s maximum efficiency (EC50)
What is the definition of the efficacy of a drug
The efficacy of a drug refers to the maximum potential therapeutic effect of a drug over any concentration
What is the definition of an agonist
An agonist is any compound (could be a drug, endogenous molecule, etc) that keeps a receptor in an active state
What is the definition of an antagonist
An antagonist is any compound (could be a drug, endogenous molecule, etc) that inhibits the action of an agonist but has no effect on its own (i.e. without an agonist)
What factors influence the occupation of a receptor by a ligand (agonist,antagonist or inverse agonist)
Factors such as concentration, competition (direct) and affinity of a ligand for influence the occupation of a receptor
What factors influence the activation of a receptor by a ligand (agonist,antagonist or inverse agonist)
Factors such as the efficacy, competition (indirect) and inverse agonist can affect the activation of a receptor
What is the difference between a competitive and a non-competitive agonist? What is the name given to a non competitive antagonist
A competitive antagonist occupies the binding site of a receptor. A non competitive antagonist does no occupy the binding site and are called allosteric competitors
What are partial agonists
Partial agonists cause a response in a receptor that is smaller than that caused by a ‘full’ agonist. Poor partial agonists can act as competitive antagonists
What is the effect of a reversible competitive antagonist on efficacy and potency of a drug
A reversible competitive antagonist does not affect the efficacy of a drug but reduces potency
What is the effect of an irreversible competitive antagonist on efficacy and potency of a drug
An irreversible competitive antagonist generally reduces efficacy but does not affect potency. However in some cases potency can also be affected
What is an inverse agonist
Inverse agonists change a receptor from an active state to an inactive state. They inhibit the basal response of an inactive receptor
What is the difference between an inverse agonist and an antagonist
An inverse agonist inhibits the basal response of a receptor (i.e. the response in absence of agonist). An antagonist inhibits the affect of an agonist but has no affect in it’s absence
What is the therapeutic index of a drug
Therapeutic index describes the range in concentration of a drug from the ED50 (therapeutic potency) and TD50(toxic dose potency)
What is the formula for the therapeutic index of a drug
TI= toxic potency - potency
