ch 2: principles of drug action

Question 1

drug administration

Answer 1

method by which a drug dose is made available to the body –> identifies drug dosage forms and routes of administration

Question 2

enteral

Answer 2

refers literally to the small intestine, but is also more broadly applicable to administration of drugs intended for absorption anywhere along the gastrointestinal tract

Question 3

systemic effect

Answer 3

pertains to the whole body, whereas the target for the drug is not local, possibly causing side effects

Question 4

parenteral

Answer 4

“besides the intestine”, administration of a substance in any way other than the intestine, most commonly an injection

Question 5

transdermal

Answer 5

drugs formulated for application to the skin, use of the skin, this route can supply long-term continuous delivery to the systemic circulation

Question 6

inhalation

Answer 6

taking a substance, typically in the form of gases, fumes, vapors, mists, aerosols, or dusts, into the body by breathing in –> can have a systemic or local effect

Question 7

local effect

Answer 7

limited to the area of treatment

Question 8

topical

Answer 8

use of the skin or mucous membrane, drugs applied directly to skin

Question 9

5 layers of the lower respiratory tract

for drug absorption

Answer 9

1. airway surface liquid
2. epithelial cells
3. basement membrane
4. interstitium
5. capillary vascular network

Question 10

aqueous diffusion

Answer 10

occurs in the aqueous compartments of the body, such as interstitial spaces or within a cell

Question 11

lipid diffusion

Answer 11

occurs across epithelial cells with lipid membranes. For a drug to be distributed in the body, it must cross the many epithelial membranes that have lipid membranes before it reaches the target organ

Question 12

carrier-mediated transport

Answer 12

occurs by special membrane-embedded carrier molecules transporting substances across membranes

Question 13

bioavailability

Answer 13

the proportion of the drug that reaches the systemic circulation

Question 14

minimal inhibitory concentration (MIC)

Answer 14

the lowest concentration of a drug at which a microbial population is inhibited

Question 15

drug distribution

Answer 15

the process by which a drug is transported to its sites of action, is eliminated, or is stored

Question 16

volume of distribution

Answer 16

Drug amount and the plasma concentration can change this –> important for estimating the dose needed for a given therapeutic level of drug

Question 17

liver

Answer 17

the main organ for drug metabolism

Question 18

kidney

Answer 18

the primary site for drug excretion

Question 19

cytochrome P450 oxidase system

Answer 19

the major enzyme system in the liver

Question 20

first-pass effect

Answer 20

initial metabolism in the liver of a drug taken orally before the drug reaches the systemic circulation

Question 21

clearance

Answer 21

a measure of the ability of the body to rid itself of a drug

Question 22

plasma clearance

Answer 22

refers to a hypothetical volume of plasma that is completely cleared of a drug over a given period

Question 23

plasma half-life

Answer 23

the time required for the plasma concentration of a drug to decrease by one half

Question 24

lung availability/total systemic availability ratio (L/T ratio)

Answer 24

amount of drug that is made available to the lung out of the total available to the body

Question 25

structure-activity relationship (SAR)

Answer 25

the relationship between the chemical structure of a drug and its clinical effect or activity

Question 26

four mechanisms for transmembrane signaling

Answer 26

1. lipid-soluble drugs cross the cell membrane and act on intracellular receptors to initiate the drug response
2. the drug attaches to the extracellular portion of a protein receptor, which projects into the cell cytoplasm and activates an enzyme system, such as tyrosine kinase, in the intracellular portion to initiate an effect
3. the drug attaches to a surface receptor that regulates the opening of an ion channel
4. the drug attaches to a transmembrane receptor that is coupled to an intracellular enzyme by a G protein

Question 27

therapeutic index (TI)

Answer 27

difference between the minimal therapeutic and toxic concentrations of a drug; the smaller the difference, the greater chance the drug will be toxic

Question 28

agonist

Answer 28

a drug or chemical that binds to a corresponding receptor and initiates a cellular effect or response

Question 29

antagonist

Answer 29

a drug or chemical that is able to bind to a receptor but causes no response

Question 30

chemical antagonism

Answer 30

direct chemical interaction between a drug and biologic mediator that inactivates the drug

Question 31

functional antagonism

Answer 31

can occur when two drugs each produce an effect and the two effects cancel each other

Question 32

competitive antagonism

Answer 32

occurs when a drug has affinity for a receptor but no efficacy and at the same time blocks the active agonist from binding to and stimulating the receptor

Question 33

synergism

Answer 33

occurs when two drugs act on a target organ by different mechanisms of action, and the effect of the drug pair is greater than the sum of the separate effects of the drugs

Question 34

additivity

Answer 34

occurs when two drugs act on the same receptors, and the combined effect is the simple linear sum of the effects of the two drugs, up to a maximal effect

Question 35

potentiation

Answer 35

a special case of synergism in which on drug has no effect but can increase the activity of the other drug

Question 36

idiosyncratic effect

Answer 36

effect that is the opposite of, or unusual, or an absence of effect, compared with the predicted usual effect in an individual

Question 37

hypersensitivity

Answer 37

allergic or immune-mediated reaction to a drug, which can be serious, requiring airway maintenance or ventilatory assistance

Question 38

tolerance

Answer 38

decreasing intensity of response to a drug over time

Question 39

tachyphylaxis

Answer 39

rapid decrease in responsiveness to a drug