pharmacodynamics

Question 1

pharmacodynamics

Answer 1

what the drug does to the body and how they do it; the study of biochemical and physiologic actions of drugs and the molecular mechanisms by which those effects are produced.

Question 2

dose response relationship

Answer 2

the relationship between the size of an administered dose and the intensity of the response produced; the minimum amount of drug needed to elicit a response and the maximum response a drug can elicit, how much to increase the dosage to increase the response

Question 3

drug responses are…

Answer 3

graded-patient response gets more intense with increased dosing

Question 4

efficacy

Answer 4

maximum efficacy: largest effect that a drug can produce

Question 5

potency

Answer 5

amount of drug given to elicit an effect. a potent drug produces its effects at low doses

Question 6

efficacy and potency

Answer 6

two drugs can be equally effective but have different potency

Question 7

drug receptors

Answer 7

chemical sites in the body that drugs interact with to produce effects-make selective drug action happen. drugs either mimic or block the action of the body’s own regulatory molecules; do NOT give cells new functions; drugs produce their therapeutic effects by helping the body use its pre-existing capacities

Question 8

drug receptors and selectivity: what happens when a drug interacts with one type of receptor that regulates only few processes?

Answer 8

the effects of the drug will be limited

Question 9

drug receptors and selectivity: what happens when a drug interacts with a receptor type that regulates multiple processes?

Answer 9

the drug is likely to elicit a variety of responses

Question 10

drug receptors and selectivity: what happens when a drug interacts with multiple receptors?

Answer 10

it will elicit a variety of responses

Question 11

affinity

Answer 11

strength of attraction between a drug and its receptor

Question 12

high affinity drugs have…

Answer 12

high affinity drugs have a strong attraction for receptor sites. they are very potent

Question 13

low affinity drugs need…

Answer 13

low affinity drugs need to be present in high concentrations to elicit a response

Question 14

intrinisic activity

Answer 14

the ability of a drug to activate a receptor upon binding

Question 15

high intrinsic activity

Answer 15

drugs with high intrinsic activity have high maximal efficacy and produce and intense response

Question 16

agonists

Answer 16

activate receptors; have high affinity and intrinsic activity. they mimic action of endogenous regulators

Question 17

antagonists

Answer 17

they prevent receptor activity: high affinity but no intrinsic activity. they bind to receptors but do not cause receptor activation. they block actions of endogenous regulatory molecules or drugs

Question 18

response to an antagonist is determined by

Answer 18

how much agonist is present

Question 19

types of antagonists

Answer 19

noncompetitive antagonists and competitive antagonists

Question 20

noncompetitive antagonsits

Answer 20

bind irreversibly to receptors and decrease the total number of receptors available for binding

Question 21

competitive antagonists

Answer 21

produce receptor blockage by competing with agonists. if both have equal affinity then the receptor is occupied by whichever agent is higher in concentration

Question 22

partial agonists

Answer 22

an agonist with moderate intrinsic activity. produces less effect than a full agonist

Question 23

example of partial agonists

Answer 23

pentazocine (a partial agonist) and meperidine (a full agonist)- better pain relief with meperidine

Question 24

regulation of receptor sensitivity: desensitization

Answer 24

desensitization (refractoriness) results from continuous exposure of cell receptors to an agonist: the cell is less responsive + implications for drug tolerance

Question 25

regulation of receptor sensitivity: hypersensitivity

Answer 25

hypersensitivity results from continuous exposure of cell receptors to antagonist: the cell is hypersensitive

Question 26

drug responses without a receptor

Answer 26

react through physical or chemical reactions: antacids, saline laxatives, chelating agents

Question 27

safety in drug dosing: average effective dose (ED50)

Answer 27

dose required to produce a defined therapeutic response in 50% of the population. patients must be evaluated individually for the proper dosing-many variables

Question 28

safety in drug dosing: therapeutic index (ED50:LD50)

Answer 28

ratio between average effective dose and average lethal dose. wide therapeutic index is relatively safe. narrow therapeutic index is relatively unsafe

Question 29

3 possibilities of drug-drug interactions

Answer 29

one drug intensifies the effects of the other, one drug reduces the effects of the other, the combination produces a new response not seen with either drug alone

Question 30

mechanisms of drug-drug interactions

Answer 30

direct chemical or physical interactions, pharmacokinetic interactions (altered absorption, altered distribution-competition for protein binding), altered metabolism (enzyme induction or enzyme inhibition), altered renal excretion

Question 31

mechanisms of drug-drug interactions pt 2

Answer 31

pharmacodynamic interactions: drugs act at the same site, drugs act at separate sites; combined toxicity. the more drugs a patient receives the greater the chance there will be an interaction

Question 32

drug-food interactions

Answer 32

food and drugs may interact to alter the effect of pharmacotherapy: decreased or increased absorption. risk for toxicity may increase with drug food interactions. drug action may be decreased

Question 33

timing with respect to meals

Answer 33

administration on an empty stomach: 1 hour before or 2 hours after eating
administration with food: with food or shorty after

Question 34

the grapefruit juice effect

Answer 34

grapefruit juice inhibits an isoenzyme responsible for intestinal metabolism of multiple drugs. this inhibitory effect is dependent on the amount of juice consumed and can persist for up to 3 days. it increases amount of drug available for absorption which increases the blood level of drugs. patient teaching point.

Question 35

drug-herb interactions

Answer 35

drug interactions may also result from herbal supplements interacting with drugs. they can impact therapeutic outcome of prescribed agents (increased toxicity, reduced therapeutic outcomes)