PHARMACOLOGY-pharmacodynamics Flashcards
Pharmacodynamics is the study of…
effect site concentration and clinical effect
What the drug does to the body
What is pharmacokinetics
What the body does to the drug
i.e. plasma concentration, absorption, distribution, metabolism, elimination
What is pharmacobiophasics
The specific area of the body where the drug engages tis receptor
Drug concentration in the biophase (not plasma) determines its clinical effect
What does the dose-response curve illustrate
The relationship between the drug dose and its clinical effects.
Describes potency, efficacy, and slope
Define potency
The dose required to achieve a given clinical effect
What do the ED 50 and ED90 measure and represent
Measure = potency Represent = the dose required to achieve a given effect in 50% and 90% of the population
Define efficacy
Ability of a drug to elicit a given clinical effect
When is risk for drug toxicity increased
Once a drug dose reaches maximum efficacy but additional administration are given…
What does the slope of the dose-response curve depict
How many receptors must be occupied to elicit a clinical effect
Define “individual variability”
Differences between PK and PD between patients
What pharmacokinetic factors affect potency
absorption, distribution, metabolism, elimination, and receptor affinity
What does a left-shift in the dose-response curve represent (3)
Increase affinity for receptor
Higher potency
Lower dose required
What does a right-shift in the dose-response curve represent (3)
Decreased affinity for receptor
Lower potency
Higher dose require
What does a higher plateau on the dose-response curve imply
Greater efficacy of a drug
What does a low plateau on the dose-response curve imply
Lower efficacy of a drug
What happens once the plateau phase is reached on the dose-response curve
Additional drug canNOT produce additional effects and increase the risk of toxicity
What does a steep slope of the dose-response curve imply
That most receptors must be occupied before we observe the clinical response
How does a full agonist drug work
Example drug
It instructs the receptor to produce its maximal response by mimicking an endogenous ligand
Ex = norepinephrine, dopamine, propofol, alfentanil
How does a partial agonist work.
Example drug
They are capable of partially activating a cellular response when binding to a receptor. It is less efficacious than a full agonist
Ex = nalbuphine
How does an antagonist work
By binding to a receptor and preventing an agonist from binding. It prevents the receptor from having any response
What is the difference between competitive and noncompetitive antagonism
Competitive = reversible Noncompetitive = NOT reversible, permanently binds receptor via covalent bonds
What are examples of drugs that are competitive antagonists
Atropine
Nondepolarizing NMBD
What are examples of drugs that are noncompetitive antagonists
Aspirin
Phenoxybenzamine
How does an inverse agonist work
Example of drug
By binding to the receptor and causing the opposite effect of the full agonist
Ex = propranolol
What effect can occur with continuous administration of an antagonist
Up-regulation of the target receptors
How can a competitive antagonist action be overcome
By increasing the concentration of the agonist
How is the dose-response curve of an agonist affected by a competitive antagonist
Since more drug would be required to reach clinical effect, the curve would appear as a reduction in potency (right shift)
How is the dose-response curve of an agonist affected by a noncompetitive antagonist
The curve is shift down, resembling a partial agonist
How are the effects of noncompetitive antagonists reversed
By producing new receptors
fyi administering increased agonist drugs will not cause the agonist to out-compete and displace the noncompetitive drug
What type of efficacy do inverse agonists have
Negative efficacy
What are the 4 possible responses with coadministration of drugs
Addition
Synergism
Potentiation
Antagonism
Describe the behavior of addition with coadministration of drugs
Given an example
Effect of two drugs given at the same time are added together
1+1=2
Morphine + dilaudid
ASA + ibuprofen
Describe the behavior of synergism with coadministration of drugs
Give an example
Effect of two drugs given at the same time is GREATER than the sum of their individual effects
1+1=3
Propofol + midazaolam
Levodopa + carbidopa
Describe the behavior of potentiation with coadministration of drugs
Give an example
Effect of one drug is enhanced by the drug that has no effect of its own
1+0=3
PCN + probenecid
Describe the behavior of antagonism with coadministration of drugs
Give an examples
Simultaneous administration of one drug negates the effect of the second drug
1+1=0
Midazolam + flumazenil
Fentanyl + naloxone
Define ED50 (effective dose 50)
the dose that produces the expected clinical response in 50% of the population
Define LD50 (lethal dose 50)
The dose that produces death in 50% of the population
Define TD50 (toxic dose)
The dose that produces toxicity in 50% of the population
What is therapeutic index and what does it measure
The measure of drug safety
It’s a ratio between either LD50 or TD50 to ED50
What is the ED50 a measure of
POTENCY
The dose that produces the expected clinical response in 50% of the population
Describe the margin of safety in a drug that has either a narrow or wide therapeutic index
Narrow TI = narrow margin of safety (lower TD50:ED50 ratio)
Wide TI = wide margin of safety (higher TD50:ED50 ratio)
Define chirality
Tetrahedral bonding of carbon to 4 DIFFERENT atoms
What are enantiomers
Chiral molecules that are non-superimposable mirror images of another
This affects receptors that may be sterospecific
How are R and S enantiomers related.
They are mirror images of each other. Not superimposable
Give an example of drugs that have R and S enentiomers
Ketamine
Isoflurane
Morphine
How does manipulation of the ratio of R and S enantiomers affect a medication
It can manipulate certain side effects
What are racemic mixtures
They contain 2 enantiomers in equal amounts i.e. racemic epinephrine
How does the amount of chiral carbons relate to enantiomers
The more chiral carbons means the more enantiomers that can be created
