Pharmacodynamics Flashcards
1
Q
define pharmacokinetics
A
- the study of absorption, distribution, metabolism and excretion of drugs
2
Q
define pharmacodynamics
A
- the study of effects of drugs and their mechanisms of action
3
Q
define Emax and EC50
A
- Emax is the maximal response produced by the drug
- EC50 is the drug concentration that produces 50% of the maximal effect
4
Q
define spare receptors and how Kd and EC50 are affected
A
- With spare receptors, it seems that EC50 < Kd
- this is because of signal amplification with one ligand
5
Q
define efficacy and potency
A
- efficacy is the maximum effect a drug can produce (Emax)
- potency is a measure of the concentration or amount of drug necessary to produce an effect of a given magnitutde
- EC50 usually used to determine potency
- potency is less important
6
Q
describe competitive antagonism
A
- competitive antagonists bind to the agonist binding site on the receptor
- shifts the curve to the right
- high concentrations of agonist can surmount the effect of a given concentration of the antagonist
- the Emax for the agonist remains the same
7
Q
describe irreversible competitive antagonism
A
- a receptor bound by an irreversible antagonist cannot respond to the binding of an agonist
- this is insurmountable
- the Emax of the agonist is reduced
8
Q
describe noncompetitive antagonism/allosteric
A
- noncompetitive antagonists bind to the receptor at a site different from the agonist binding site
- insurmountable
- antagonist binding reduces the action of the agonist
- Emax is decreased
- identical graph to irreversible competitive antagonist
9
Q
describe indirect antagonism
A
- the antagonist binds to a macromolecule in the pathway that links the receptor to the effect
- for example: a drug that inhibits PKA blocks the effects of a B-adrenoreceptor agonist
10
Q
define physiological antagonism
A
- one drug opposes another drug, but through different receptors
- epinephrine increases bp and causes bronchodilation
- histamine decreases bp and causes bronchoconstriction
11
Q
define chemical antagonism
A
- a chemical antagonist reacts chemically with an agonist to form an inactive product
- for example, protamine (positively charged) counteracts the effects of heparin (negatively charged)
12
Q
describe desensitization/tachyphylaxis
A
- the effect of a drug gradually dimishes when given continuosly or repeatedly
13
Q
describe quantal dose-effect curves
A
- the quantal-dose response relationship plots the fraction of the population that responds to a given dose of drugs as a function of the drug dose
- the responses are either present or not present
14
Q
describe the median effective dose (ED50)
A
- the dose at which 50% of individuals exhibit the specified quantal effect
15
Q
describe TD50 and LD50
A
- the dose required to produce a particular toxic effect in 50% of animals is called the median toxic dose (TD50)
- the dose required to cause death in 50% of animals is called the median lethal dose