week 5- pharmacodynamics

Question 1

pharmacodynamics

Answer 1

study of the physiologic and biochemical effects that drugs have on the body and how those effects are produced

Question 2

why is pharmacodynamics important for nurses?

Answer 2

• allows us to properly educate patients, evaluate effectiveness and administer PRN meds
• provides foundation for challenging a prescription

Question 3

dose-response curve

Answer 3

phase 1: no measurable response
phase 2: inc in dose/inc in response
phase 3: plateau where an inc in dose leads to no change in effect

Question 4

maximal efficacy

Answer 4

the largest effect that a drug can produce, indicated by the height of the dose-response curve

Question 5

potency

Answer 5

the amount of drug needed to elicit a response, indicated by the relative position of the dose-response curve along the x axis

Question 6

receptors

Answer 6

• functional macromolecules inside or on the surface of a cell where a ligand can bind
• any part of the cell can be a macromolecule that acts as a receptor

Question 7

ligand

Answer 7

any chemical that binds to a receptor

Question 8

drugs

Answer 8

chemicals that produce an effect by interacting with other chemicals in the body

Question 9

drug-receptor complexes

Answer 9

drugs can only mimic or block the action of a specific receptor

Question 10

types of receptors

Answer 10

cell-membrane embedded enzymes, ligand-gated ion channels, G protein-coupled receptor systems, transcription factors

Question 11

cell membrane embedded enzymes

Answer 11

• span the cell membrane
• enzymes located inside the cell
• ligand binds to cell surface, activating the enzyme
• response within seconds

Question 12

ligand-gated ion channels

Answer 12

• span the cell membrane
• used for regulating the flow of ions across the membrane
• ion flow is dependent on concentration gradient
• response within milliseconds

Question 13

g-protein coupled receptors

Answer 13

• three components; receptor, G protein and effector
• ligand binding leads to activation of receptor, which then activates G protein, which then activates the effector
• rapid response

Question 14

transcription factors

Answer 14

• receptor is located within the cell
• ligand binds to a receptor on the DNA (within nucleus)
• response is the transcription of mRNA
• response takes hours to days

Question 15

receptor selectivity

Answer 15

• lock and key model
• only specific ligands can bind, leading to selective responses

Question 16

example of side effects from non-selective receptors- epinephrine and alpha 1

Answer 16

• when binding to alpha 1, epinephrine should lead to inc HR
• however, the receptor is non-selective
• binding also controls pupil dilation, increased BP and slowed gastric motility

Question 17

single occupancy theory

Answer 17

• states the the intensity of the response to a drug is proportional to the number of receptors occupied by that drug and a maximal response will occur when all available receptors have been occupied
• can’t explain potency or maximal efficacy

Question 18

modified occupancy theory

Answer 18

• explains certain observations that the simple occupancy theory cannot
• the simple occupancy theory assumes that all drugs acting at a receptor are identical with respect to the ability to bind to the receptor and the ability to influence receptor function once binding has taken place
• drugs have two properties; affinity and intrinsic activity

Question 19

affinity

Answer 19

strength of the attraction between a drug and its receptor, this is reflected in a drug’s potency (high affinity = very potent)

Question 20

intrinsic activity

Answer 20

the ability of the drug to activate the receptor after binding, this is reflected in a drug’s maximal efficacy (high intrinsic activity = high efficacy)

Question 21

drug categories

Answer 21

agonists, partial agonists, competitive antagonists, non-competitive antagonists

Question 22

agonist

Answer 22

mimics an endogenous ligand, has both high affinity and intrinsic activity
ie. insulin

Question 23

partial agonist

Answer 23

only has moderate intrinsic activity, maximum effect is half that of an agonist

Question 24

antagonist

Answer 24

• no intrinsic activity, blocks agonist from binding
• high affinity
• outcome is dependent on amount of agonist present
  ie. narcan

Question 25

non-competitive antagonist

Answer 25

bind irreversibly to receptors, so they cannot be overcome by adding more agonist (reduces maximal response of an agonist)

Question 26

competitive antagonist

Answer 26

reversibly binds receptors, can be overcome by adding more agonist (competes with agonist)

Question 27

drug-receptor sensitivity

Answer 27

- cells can become desensitized when receptors are continually exposed to an agonist (dec # of receptors/dec response) - cells can becomes hypersensitized when receptors are continually exposed to an antagonist (inc # of receptors)

Question 28

ED50

Answer 28

- dose required to produce an effect in 50% of the population - often given as the initial dose when starting a medication

Question 29

LD50

Answer 29

dose required to produce toxic effects in 50% of the population

Question 30

therapeutic index

Answer 30

measures the safety of a drug, larger TI=safer TI = LD50/ED50

Question 31

bioavailability

Answer 31

- amount of active drug that reaches systemic circulation from the administration site - important to know for drugs with narrow TI

Question 32

pharmacogenomics

Answer 32

- study of how genetics impact a person's response to medications, metabolism is the most common genetic difference - slow metabolism can lead to accumulation and toxicity, fast metabolism can lead to sub-therapeutic effect

Question 33

other genetic variations

Answer 33

- altering drug receptors - gender differences ie. viagra inhibits PDE5, causing vasodilation in lungs and penis (reduces pulmonary HT)