Drug Action Flashcards
1
Q
Absorption
A
movement of drug particles from the GI tract to the body fluids by passive absorption, active absorption, or pinocytosis
2
Q
most oral drugs are absorbed…
A
into the surface area of the small intestine through the action of the extensive mucosal villi
3
Q
What happens to absorption if the villi decreases?
A
Absorption decreases because of disease, drug, effect or the removal of the small intestine
4
Q
What happens to protein-based drugs in the small intestine?
A
they are destroyed by digestive enzymes
5
Q
passive absorption
A
-occurs mostly by diffusion -does not require energy to move across the membrane
6
Q
diffusion
A
movement from high concentration to lower concentration
7
Q
active absorption
A
-requires a carrier as an enzyme or protein to move the drug against the concentration gradient -energy required
8
Q
pinocytosis
A
process by which cells carry a drug across the membrane by engulfing the drug particles
9
Q
GI membrane is composed of…
A
mostly lipid (fat) and protein
10
Q
Drugs that are __________ pass rapidly through the GI membrane
A
lipid-soluble
11
Q
________ need a carrier to pass through the membrane
A
water-soluble
12
Q
Large particles pass through cell membrane if…
A
they are nonionized
13
Q
nonionized
A
no positive or negative charge
14
Q
weak acid drugs are..
A
less ionized in the stomach and they pass through the stomach lining easily and rapidly
15
Q
an infant’s GI secretions are..
A
higher pH (alkaline) than those of adults
16
Q
drugs that are _____ and _______ are absorbed faster than _______ and ________
A
-lipid-soluble, nonionized -water-soluble, ionized
17
Q
What can affect drug absorption?
A
-blood flow -pain -stress -hunger -fasting -food -pH
18
Q
Poor circulation to the stomach…
A
hampers absorption
19
Q
What could cause poor circulation to the stomach?
A
result of shock, vasoconstrictor drugs, or disease
20
Q
What could cause slow gastric emptying time?
A
-pain -stress -foods that are solid, hot, or high in fat
21
Q
What is bad about a slow gastric emptying time when it comes to medication?
A
drug remains in stomach longer
22
Q
exercise can…..
A
decrease blood flow by causing more blood to flow to the peripheral muscle, thereby decreasing blood circulation to the GI tract
23
Q
Drugs given IM…
A
are absorbed faster than subQ due to there being more blood vessels in the muscle
24
Q
Drugs are absorbed faster in the deltoid due to…
A
very vascular
25
Some drugs do not go directly into the systemic circulation following oral absorption....
they pass from the intestinal lumen to the liver via the portal vein
26
In the liver, what happens to drugs?
first-pass effect
27
first-pass effect
process in which the drug passes to the liver first
1. drug is metabolized to inactive form that may be excreted, thus reducing the amount of active drug
2. do not undergo any metabolism
3. drug is metabolized to drug metabolite, which may be equally or more active than the original drug
28
most drugs given orally are...
affected by first-pass metabolism
29
bioavailability
-subcategory of absorption -% of drug administered that reaches the systemic circulation
30
for oral route, bioavailability...
occurs after absorption and first-pass metabolism
31
The % of bioavailability for the oral route is...
always less than 100%
32
The % of bioavailability for the IV route is...
100%
33
Oral drugs that have a high first-pass metabolism...
may have availability of only 20% to 40% on entering systemic circulation
34
To obtain the best drug effect, oral dose could be...
higher than the drug dose for IV use
35
Factors that alter bioavailability
1. drug form 2. route 3. GI mucosa and motility 4. food and other drugs 5. changes in liver metabolism caused by liver dysfunction or inadequate hepatic blood flow
36
decreased liver function or decreased hepatic blood flow....
leads to increased bioavailability of a drug, but only if the drug is metabolized by the liver -less drug is destroyed by the hepatic metabolism in the presence of liver disorder
37
With some oral drugs, rapid absorption...
increases the bioavailability of the drug and can cause an increase in drug concentration -drug toxicity may result
38
slow absorption can...
limit the bioavailability of the drug, thus causing a decrease in drug serum concentration
39
Distribution
process by which the drug becomes available to body fluids and body tissues
40
Distribution is influenced by..
-blood flow -drug's affinity to the tissue -protein-binding effect
41
protein-binding effect
as drugs are distributed in the plasma, many are bound to varying degrees with protein
42
Vd
Volume of drug distribution -dependent on drug dose and its concentration in the body
43
drugs with larger volume of drug distribution....
have a longer half-life and stay in the body longer
44
\>89% bound to protein
highly protein-bound drugs
45
61%-89% bound to protein
moderately highly protein-bound drugs
46
30%-60% bound to protein
moderately protein-bound drugs
47
free active drug
-drugs not bound to protein -active and can cause a pharmacologic response
48
the portion of the drug that is bound to protein is...
inactive and not available to receptors
49
as the free active drug decreases over time...
more bound drug is released from the protein to maintain the balance of free drug
50
bound drugs cannot...
leave systemic circulation to get to site of action
51
When two highly protein-bound drugs are given concurrently...
they compete for protein-binding sites, thus causing more free drug to be released into circulation
52
What could result from two highly protein-bound drugs given at the same time?
drug accumulation and possible drug toxicity
53
low serum protein level decreases...
the number of protein-binding sites
54
low number of protein-binding sites can cause...
increase in the amount of free drug in the plasma and drug toxicity may result
55
drug is dosed and prescribed according to...
the % in which the drug binds to protein
56
Who would have low serum albumin levels?
-patients with liver or kidney dz -malnourished patients
57
Who is more likely to have hypoalbuminemia?
OAs
58
with some health conditions that result in low serum protein levels....
excess free or unbound drug goes to nonspecific tissue binding sites until needed -excess free drug in the circulation does not occur
59
To avoid possible drug toxicity, checking the...
protein-binding % of all drugs administered to a patient is important
60
RN should check pt's plasma protein and albumin levels because...
a decrease in plasma protein (albumin) decreases the available protein-binding sites, permitting more free drug in the circulation -could be life threatening based on drug
61
What hinders drug distribution?
-abscesses -exudates -body glands -tumors
62
\_\_\_\_\_\_\_ do not distribute well at abscess and exudate sites
antibiotics
63
some drugs accumulate in particular tissues such as...
-fat -bone -liver -muscle -eye tissues
64
BBB
blood brain barrier -semipermeable membrane in the CNS that protects the brain from foreign substances
65
\_\_\_\_\_\_\_\_\_\_\_\_ drugs are able to cross the BBB
highly lipid-soluble
66
What type are drugs are not able to cross the BBB?
-drugs not bound to proteins -drugs that are not lipid-soluble
67
What is made difficult by drugs not being able to cross the BBB?
it is difficult to distribute the drug
68
During pregnancy, what type of drugs are able to cross the placental barrier?
both lipid-soluble and lipid-insoluble drugs -can affect both fetus and mother
69
What is considered before administering drugs to pregnant mothers?
risk-benefit ratio
70
During lactation, drugs...
can be secreted into breast milk -could affect the nursing infant
71
RNs responsibility when it comes to administering meds to breast feeding mother?
check which drugs may cross into breast milk
72
Metabolism
process by which the body inactivates or biotransforms drugs
73
Drugs can be metabolized....
in several organs, but liver is PRIMARY SITE OF METABOLISM
74
Most drugs are ______ by liver enzymes
inactivated -then converted or transformed by hepatic enzymes to inactive metabolites or water-soluble substances for excretion
75
Large % of drugs are \_\_\_\_\_\_\_\_\_\_
lipid-souble
76
lipid-soluble drugs are metabolized by the liver....
into a water-soluble substance for renal excretion
77
Half-Life
time it takes for 1/2 of the drug concentration to be elminiated
78
What affects the half-life of a drug?
metabolism and elimination
79
liver or kidney dysfunction leads to...
prolonged half-life and less drug is metabolized and elminiated
80
Drugs go through...
several half lives before more than 90% of the drug is eliminated
81
Longer the half-life...
longer to leave the body
82
By knowing the half-life,
you can compute the time it takes for a drug to reach a steady state of serum concentration
83
how many half-lives does it take to saturate the biologic system to the extent that the intake of the drug equals the amount metabolized and excreted?
3 to 5 half-lives
84
Main route of drug elimination is through...
the kidneys/urine
85
other elimination routes are...
-bile -feces -lungs -saliva -sweat -breast milk
86
Kidneys filter....
free unbound drugs, water-soluble drugs, and drugs that are unchanged
87
Lungs eliminate...
volatile drug substances and products metabolized to CO2 and H2O
88
urine pH influences...
drug excretion
89
urine pH varies from
4.5 to 8
90
acidic urine
promotes elimination of weak base drugs
91
alkaline urine
promotes elimination of weak acid drugs
92
ASA
weak acid -rapidly excreted in alkaline urine
93
With kidney disease that results in decreased GFR or decreased renal tubular secretion....
drug excretion is slowed or impaired
94
decreased blood flow to kidneys....
alters drug excretion
95
common tests used to determine renal function
-CLcr -BUN
96
CLcr
compares the level of creatinine in the URINE with the level of creatinine in the BLOOD -varies with age and gender
97
Who is expected to have decreased CLcr values?
OA and females because of their decreased muscle mass
98
GFR
may be the best test, but very expensive and not so commonly used
99
decreased GFR results in....
increase in serum creatinine level and a decreased in CLcr
100
renal dysfunction in OA
drug dosage usually needs to be decreased -CLcr needs to be determined to establish appropriate drug dosage
101
creatinine
metabolic by-product of muscle that is excreted by the kidneys
102
Pharmacodynamics
study of the way drugs affect the body
103
drugs can cause...
primary or secondary effect (or both)
104
primary effect
desired
105
secondary effect
desired or undesired
106
drug response
relationship between the minimal vs. maximal amount of drug dose needed to produce the desired drug response
107
all drugs have a....
maximum drug effect or maximal efficacy
108
Tramadol vs. Morphine
Morphine has a greater maximal efficacy -no matter how much tramadol is given, it will never be as great as Morphine when controlling pain
109
onset of action
time it takes to reach the minimum effective concentration (MEC) after a drug is adminitered
110
peak action
occurs when the drug reaches its highest blood or plasma concentration
111
duration of action
length of time the drug has a pharmacologic effect
112
time-response curve
evaluates 3 parameters of drug action: -onset -peak -duration
113
if plasma or serum level decreases below threshold or MEC....
adequate drug dosing is not acheived
114
If drug plasma or serum level increases above threshold or MEC...
can result in toxicity
115
Receptor theory
drugs act through receptors by binding to the receptor to produce (initiate) a response or to block (prevent) a response
116
Activity of many drugs is determined by...
the ability of the drug to bind to a specific receptor
117
the better the drug fits into the receptor...
the more biologically active the drug is
118
most receptors are....
protein in nature and found in cell membranes
119
drug-binding sites are primarily on...
- proteins
- glycoproteins
- proteolipids
- enzymes
120
agonists
produce response
121
antagonists
block a response
122
Epiniephrine stimulates beta1 and beta2 receptors, so...
it is an agonists
123
Atropine blocks histamine receptor, so...
it is an antagoinist
124
Effects of an antagonist can be determined by...
the inhibitory action of the drug concentration on the receptor site
125
Cholinergic receptors are located...
- bladder
- heart
- blood vessels
- stomach
- bronchi
- eyes
126
nonspecific drugs
drugs that affect various sites and have nonspecificity properties
-evoke a variety of responses throughout the body
127
nonselective drugs
affect various receptors or have properties of nonselectivity
-produce a response but do not act on a receptor may act by stimulating or inhibiting enzyme activity or hormone production
128
categories of drug action
1. stimualtion
2. replacement
3. inhibition
4. irritation
129
Therapeutic Index
estimates the margin of safety of a drug through the use of a ratio that measures the effective dose in 50% of people and the lethal dose in 50% of people
-closer to 1, the greater danger of toxicity
TI= LD50/ED50
130
low TI
narrow margin of safety, more dangerous
131
high TI
wide margin of safety, less dangerous
132
Serum drug levels do not need to be monitored routinely for...
drugs with high TI
133
Therapeutic range/window
drug concentration in plasma is the level of drug between the minimum effective concentration in the plasma for obtaining desired drug action and the minimum toxic concentration
134
When TR is given...
it includes both protein-bound and unbound portions of the drug
135
Increased chance of toxicity...
TR monitored
136
loading dose
when immediate drug response is desired
-large initial dose is given to achieve a rapid minimum effective concentration in the plasma
137
after loading dose...
prescribed daily dosage is ordered
138
Side effects
physiologic effect not related to desired drug effects
139
even with correct dose...
side effects occur and are predicted
140
side effects results from....
drugs that lack specificity
141
Adverse reactions
- more severe than side effects
- always undesirable
- must be report and documented
142
Adverse reaction and side effects
sometimes used interchangeably but they are different
143
RNs role with side effects
teaching patient to report any side effects
144
one of the primary reasons patients stop takinga prescribed medication
occurence of side effects
145
toxic effects or toxicity
when drug level exceeds the TR, toxic effects are likely to occue from overdosing or drug accumulation
146
For wide therapeutic index...
therapuetic ranges are seldom given
147
for narrow therapeutic index...
therapeutics ranges are closely monitored
148
Peak and trough
indicates the rate of absorption and rate of elimination
149
Peak and trough is requested for
drugs that have a narrow therapeutic index and are considered toxic
150
peak drug levels
- indicate the rate of absorption of the drug
- highest plasma concentration of drug at a specific time
151
trough drug level
- indicate the rate of elimination of the drug
- lowest plasma concentration of a drug and it measures at the rate at which the drug is eliminated
152
High P&T levels
toxicity can occur
153
low peak levels
no therapeutic effect
154
when is peak drug level drawn
at proposed peak time according to route
155
when is trough drug level drawn
immediately before next dose, regardless of route
156
drug interactions
different action or effect of a drug as result of an interaction with one or more other drugs
INSIDE THE BODY
157
drug incompatibility
chemical or physical reaction that occurs among two or more drugs within a syringe, IV bag, IV tubing
OUTSIDE THE BODY
158
absorption interactions
two or more drugs taken at the same time canc ause the absorption rate of one or more of the medications to change
159
distribution interaction
two drugs that are highly protein-bound and administered at the same time can result in drug displacement
160
metabolism
many drug interactions occur in the livers microsmal system
- enzyme inhibitors
- enzyme reducers
161
excretion
two or more drugs that undergo the same route of excretion may compete with one antoher for elminiation from the body
162
addictive drug effect
two drugs with similar actions administered at the same time
-result is the sum of the effects of the two drugs
163
synergistic drug effect
two or more drugs are given together, one can potentiate on another
-clinical effect is substantially greater than the combined effect of the two
164
antagonist drug effect
two drugs that have opposite effects are administered together, each drug cancels the effects of the other
-sometimes desired
165
drug-food interactions
-food can increase, decrease, or delay drug absorption
166
food can bind...
with drugs causing less or slower absorption
167
food may have impact on..
absorption of different dosage forms of the same drug
168
classic drug-food interaction
occurs when an antidepressant of the monoamine oxidase inhibitor type is taken with tyramine rich foods
169
tyramine rich foods
- cheese
- wine
- organ meats
- beer
- yogurt
- sour cream
- bananas
170
tyramine rich foods have what type of effect?
sympathomimetric-like
171
when tyramine rich foods are taken with antidepressants
more Norepinephrine is released leading to hypertensice crisis
172
drug-lab interactions
abnormal plasma or serum electrolyte concentrations can affect certain drug therapies
173
drug induced photosensitivity
two types: photoallergy and phototoxicity
- skin rxn caused by exposure to sunlight
- caused by interation of a drug and exposure to UVA light which can cause cellular damage
- most can be avoided with SPF
