Introduction to Pharmacodynamics Flashcards
1
Q
therapeutic index
A
- ratio of TD50 to the ED50
- provides indication of drug safety
- larger the index the safer the drug
2
Q
what is ED50?
A
effective dose in 50% of population
3
Q
what is TD50?
A
toxic dose in 50% of population
4
Q
how does a drug work?
A
- binds to receptor
- change in physical property of cell
- chemical or metabolic changes
- do not create new cell effects/actions
5
Q
drug receptor
A
- proteins on or within cell surface/cytoplasm
6
Q
ligand
A
- something that binds to a receptor
- signal molecule: endogenous substance or drug
7
Q
tachyphylaxis
A
- acute tolerance
- rapidly decreasing response to drug after only a few doses - need a drug free period to reset
8
Q
tolerance
A
- decreasing response to repeated constant doses of a drug
- may be pharmacokinetic or dynamic
- ex: opioids - if stop and restart must start at low dose or may OD
9
Q
affinity
A
- force of attraction between drug and receptor
- higher affinity drugs are harder to displace
10
Q
selectivity
A
- specificity of drug for target receptor binding
- SNS receptors
- makes fewer effects on unwanted receptors
11
Q
potency
A
- comparative term to describe concentrations of different drugs necessary to induce same magnitude of response
- a more potent drug is not necessarily a better drug
12
Q
efficacy (intrinsic activity)
A
- ability of drug to have response
- complex relationship (drug conc., receptor activation, cellular response)
13
Q
what are the 4 types of efficacy responses?
A
- agonist
- antagonist
- partial agonist
- inverse agonist
14
Q
agonist
A
- receptor interaction results in activation
- occupation theory: magnitude of response is proportional to # of receptors occupied
15
Q
partial agonists
A
- binds to receptor
- activates receptor
- only results in partial response - maximal response not observed (lower efficacy)
16
Q
antagonist
A
- drug interacts selectively with receptors, lacks intrinsic efficacy
- blocks or reduces the action of an agonist at the receptor
17
Q
2 types of antagonists
A
- competitive
- non-competitive
18
Q
competitive antagonist
A
- looks like drug, binds same site
19
Q
non-competitive
A
- binds somewhere else (allosteric site)
- changes receptor conformation so agonist cannot bind
20
Q
reversible antagonist
A
- bind to receptor (affinity) but can easily dissociate from the receptor (weak bonds like H-bonds and van der waals)
- agonist present at sufficiently high conc. can displace an antagonist
- decreases potency bc a higher conc. is now necessary to induce same response
21
Q
irreversible antagonists
A
- binds and stays
- covalent bonds
- agonist response cannot occur until receptor is replaced and any remaining unbound antagonist has been removed from body
- decreases efficacy preventing maximal possible response
22
Q
inverse agonists
A
- bind and have negative response
- receptors that have constitutive activity
- shut off cell activity
23
Q
chemical antagonism
A
- direct chemical interaction between two drugs
24
Q
physiologic antagonism
A
- two drugs act in same physiologic system but act on different receptors or pathways
25
Q
pharmacokinetic antagonism
A
- one drug alters the response to another drug through changes in disposition
26
Q
drug characteristics affecting concentration at receptor
A
- molecular weight
- lipid solubility
- pKa
- protein binding
- concentration gradient
27
Q
increased drug transfer
A
- smaller MW
- higher lipid sol.
- unionized
- lower protein binding
- higher concentration gradient