Pharmacology

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Pharmacology
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Pharmacology is the study of drugs in living
systems. It encompasses the understanding of all
medication effects, whether diagnostic,
therapeutic, or adverse. Drugs have led to the
control or cure of many medical disorders.
However, drugs have also been responsible for
many unwanted illnesses and deaths over the
years. All students of pharmacology must remember
that medications can be very helpful but can also
cause serious harm to patients. No one should
prescribe or administer medication without
knowledge and comprehension of pharmacologic
data. As a medical professional, you should learn
all that you can about the potential poisons that
will be placed into your patient. This book is
designed to teach important principles
surrounding the pharmacologic agents used
frequently in the radiologic sciences
3
Every medication has a generic name. A brand name
is given to the drug by the particular
manufacturer. Each manufacturer uses a different
brand name for its version of the generic drug.
In essence, the brand name is used as a marketing
tool. The original generic drug is developed by
one company. The developing company then acquires
a patent for exclusive rights to manufacture and
sell the generic drug as its brand drug for a
specified number of years. After the patent
expires, other companies may produce the same
generic drug under different brand names.
4
There are more than 1000 chemicals in a cup of
coffee. Of these, only 26 have been tested, and
half caused cancer in rats.
5
LEGEND DRUGS Medications that require a
prescription are called legend drugs. These all
have a written legend (or caption) on the package
stating, CAUTION Federal Law prohibits
dispensing without a prescription. Radiopaque
contrast agents and other medications
administered in the radiology department fall
into the category of legend drugs. The imaging
technologist must therefore know what constitutes
a legal prescription before dispensing or
administering drugs or diagnostic agents ordered.
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THE LEGAL PRESCRIPTION A valid prescription or
order for a drug includes at least the following
seven components 1.Patient name, room number or
address, and identification numbers 2.Drug name
(generic or brand) 3.Dosage (in proper units of
measure for particular drug) 4.Dosage form
(e.g., tablet, injection, solution) 5.Route of
administration (e.g., oral, parenteral,
rectal) 6.Date order is written 7.Prescriber's
signature
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INTRODUCTION For a drug to produce pharmacologic
effects in the body, it must first reach the site
of action. The process required for a drug to
reach the site of action is best described using
biopharmaceutic and pharmacokinetic principles.
BIOPHARMACEUTICS Biopharmaceutics is the area of
pharmacology that focuses on the method for
achieving effective drug administration. Drugs
are placed into vehicles by the manufacturing
process. A drug vehicle is a substance into which
a drug is compounded for initial delivery into
the body. A dosage formsolid, liquid, gas, or
any combination of theseis the combination of
both the drug and the vehicle used to deliver the
drug. A dosage form must be capable of releasing
its contents so that the drug can be delivered to
the site of action.
8
The bathroom medicine cabinet is one of the worst
places to keep medicines. The heat and moisture
of the bathroom are just the conditions required
to alter the chemistry of medications, making
them weaker, possibly ineffective, and in some
cases, toxic. A cool, dry area away from sunlight
and children is optimal.
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Solid dosage forms used for oral administration
include

• Tablets
• Capsules
• Troches
• Suppositories

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A tablet generally consists of an active
ingredient (drug), various fillers and
disintegrators, dyes, flavoring agents, and an
outside coating. Fillers help the powdered mass
to maintain form when compressed in the
manufacturing process. Disintegrators aid in
chemical disintegration when subjected to fluids
or temperature changes. The disintegration
process is required for the solid to become a
solution before absorption across a biologic
membrane. If something is not done to make it
dissolve, the solid will come out in the same
lump as initially used. Dyes and flavoring agents
help make the dosage form palatable. The coating
may help with palatability and aid in the
drug-releasing process.
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Various types of tablets are produced to aid in
the delivery of medication, as follows

• Compressed tablets are compacted with no special
  coating they are subject to chemical degradation
  from the environment.
• Sugar-coated tablets have a thin layer of sugar
  coating designed to mask bad taste and to protect
  the active ingredients from chemical oxidation.
• Film-coated tablets have a thin coating of
  material other than sugar. This type of coating
  serves the same function as a sugar coating but
  is less expensive to manufacture.
• Enteric-coated tablets are designed to pass
  through the gastric area and release the active
  ingredients into the small intestine. This
  technology is used to prevent the strongly acidic
  contents of the stomach from chemically
  destroying the activity of a drug. Enteric
  coating is also used to prevent gastric upset by
  a drug known to cause significant local
  irritation in the stomach.
• Multiple-compressed tablets and
  controlled-release tablets are both designed to
  mask taste, protect contents against chemical
  oxidation, and allow for periodic release of
  contents in a controlled manner throughout the
  gastrointestinal (GI) transit. Many drugs used
  for maintenance therapy, such as cardiovascular,
  pulmonary, antiepileptic, and antirheumatic
  medications, are formulated this way to allow for
  once-daily or twice-daily dosing to improve
  patient compliance.

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Effervescent tablets contain sodium bicarbonate
and an organic acid such as citrate or tartrate.
These tablets liberate carbon dioxide and
disintegrate into an effervescent solution in the
presence of water. Buccal or sublingual
tablets, such as nitroglycerin, are designed to
disintegrate in the buccal or sublingual space
and become absorbed through the buccal or
sublingual vasculature
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Capsules generally consist of either a hard or a
soft gelatin shell that encloses the active
ingredient. A hard gelatin capsule is a two-piece
shell made from calcium alginate,
methylcellulose, and gelatin. A soft gelatin
capsule is a one-piece shell made from similar
material. Capsules are designed to mask taste,
allow for ease of swallowing, and contribute to a
controlled-release mechanism. The capsule must
dissolve so that the active ingredient may be
released. Troches are generally in the form of
or pastilles. These are solids that contain
medicine in a hard sugar or glycerinated gelatin
base designed to dissolve slowly in the mouth.
Topical oral antifungals and anesthetics are most
often placed in this dosage form so that
continued contact will be made between the
medication and the oral mucosa. Compressed
suppositories or inserts are solid dosage forms
generally designed for vaginal or rectal
delivery. On contact with the mucosa and in the
presence of body temperature, these dosage forms
melt away to release the medicinal agent.
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Liquid dosage forms

• Solutions
• Emulsions
• Suspensions

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Parenteral dosage forms are given by injection
under or through one or more layers of skin or
mucous membrane. This route includes following
administrations

• Subcutaneous
• Intradermal
• Intrathecal
• Intramuscular
• Intravenous
• Intraarterial

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Intrathecal Injection
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Intravenous injection
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There are several complications that can occur
from intravenous administration

• Thrombosis formation can results from many
  factors extremes in solution pH, particulate
  material, irritant properties of the drug, needle
  or catheter trauma, and selection of too small a
  vein for the volume of solution injected
• Phlebitis, or inflammation of the vein, can be
  caused by the same factors that cause thrombosis.
• Air emboli occur when air is introduced into the
  vein. The human body is not harmed by small
  amounts of air, but a good practice is to purge
  all air bubbles from the formulation and
  administration sets before use.
• Particulate material is generally small pieces of
  glass that chip from the formulation vial or
  rubber that comes from the rubber closure on
  injection vials. Although great care is taken to
  elimination the presence of particulate material,
  a final filter in the administration line just
  before entering the venous system is a typical
  precaution.

21
Gas dosage forms are typically used for oxygen
therapy, anesthesia, and aerosol inhalers. Oxygen
is in gaseous form at room temperature and
requires no dispersing agent. Most anesthetics
are also gaseous at room temperature. The
inhalers usually contain a liquified medication
dispersed in a gas propellant, such as a
fluorinated hydrocarbon on inhaler actuation,
the fluorinated hydrocarbon gas disperses the
liquified medication to the bronchial system.
Abraham Lincoln's mother died when the family
dairy cow ate poisonous mushrooms and Mrs.
Lincoln drank the milk.
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Disintegration and Dissolution Medication is
absorbed in either liquid or gaseous solution.
Therefore, any solid or semisolid drug must first
enter into one of these solution forms before
becoming absorbed across a cellular membrane. A
medication in solid form will generally require
more time to enter the body than the same
medication in liquid form. Disintegration and
dissolution are generally considered to
constitute the beginning of the pharmacokinetic
process.
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Immediately on medication administration, a drug
begins to undergo the pharmacokinetic process.
Pharmacokinetics consists of the process of how a
drug is absorbed, distributed, metabolized, and
eliminated throughout the body. These parameters
determine the onset, duration, and extent of drug
action.
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Absorption Prior to systemic action, a drug must
either undergo the absorption process or be
administered by direct intravenous injection,
thus bypassing the need for absorption. Numerous
anatomic sites, including GI tract, lungs, mucous
membranes, eyes, skin, muscle, and subcutaneous
tissues, can be used for systemic drug absorption.
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For absorption to occur, the physiochemical
properties of the drug and the vehicle must be
compatible with the site for administration. Rate
and extent of drug absorption depend on
dissolution properties of the dosage form
(previously discussed), surface area at the site,
blood flow to the site, concentration of drug at
the site, acid-base properties surrounding the
absorbing surface, lipophilicity (attraction to
fat) of the drug, and compatibility with other
chemicals or drugs. Surface area.
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A large surface area allows for better absorption
than does a smaller area. Pulmonary alveoli and
GI rugae give rise to some of the largest surface
areas for absorption in the human body. One could
compare this concept to the distance between two
points. As the eagle flies, it may be 5 miles
from point A to point B. If you are driving in
the mountains from point A to point B, however,
you may zigzag back and forth on many curves and
actually drive 25 miles. Similarly, with lungs
and intestines, all the ins and outs add
surface area.
Some analgesic formulas, such as Alka-Seltzer and
Bromo-Seltzer, are liquid (disintegrated) when
they enter the body. This does shorten the time
between administration and onset of action (pain
relief).
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Blood flow. A large amount of blood supplies
these sites. Blood must be flowing to the
absorbing surface during the absorptive process
to allow entry into the systemic circulation.
Altered blood flow, such as occurs in
cardiovascular shock, may change the drug
absorption profile. Consequently, a patient who
is in shock generally requires medication
delivered through the intravenous route.
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Distribution Once a drug is absorbed into the
bloodstream, it is immediately distributed
throughout the body by the circulation of the
blood. Distribution is defined as the transport
of a drug in body fluids from the bloodstream to
various tissues of the body and ultimately to its
site of action.
Several factors affect distribution, as follows
1.Cardiac output amount of blood pumped by the
heart per minute. 2.Regional blood flow amount
of blood supplied to a specific organ or
tissue. 3.Drug reservoirs drug accumulations
that are bound to specific sites, such as plasma,
fat tissue, and bone tissue
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Excretion Drug molecules, whether they are intact
or metabolized, eventually must be removed from
the body. This elimination is primarily
accomplished by the kidneys. They filter the
blood and remove unbound, water-soluble
compounds. This is one reason why drug testing is
often done on urine. The intestines may also
eliminate drug compounds. After metabolism by the
liver, a metabolite may be secreted into the
bile, passed into the duodenum, and eliminated in
the feces. The third mechanism of excretion is
the respiratory system. Gases or volatile liquids
that are administered through the respiratory
system usually are eliminated by the same
route. Breast milk, sweat, and saliva also
contain certain drug compounds but are not the
body's predominant mechanisms for elimination
30
CARDIAC MEDICATIONS
Antiarrhythmic (or antidysrhythmic) medications
are those drugs that affect the electrical
conduction system of the myocardium. The actions
of these medications differ among the individual
drugs.
The ultimate goal for this class of medications
is to suppress excess electrical conduction
within the cardiac system and thus decrease
arrhythmia (dysrhythmia) production
Antihypertensive medications assist in lowering
the blood pressure to safe, long-term goals.
These drugs also affect heart failure in a
positive way by decreasing the pressure against
which the heart must pump. This allows the
failing heart to pump more efficiently without
tiring out. Many studies are now confirming the
positive long-term effects that some
antihypertensives have on the duration of life.
The first known heart medicine was discovered in
an English garden. In 1799, physician John
Ferriar noted the effect of dried leaves of the
common foxglove plant, Digitalis purpurea, on
heart action. Still used in heart medications,
digitalis slows the pulse and increases the force
of heart contractions and the amount of blood
pumped per heartbeat.
31
Diuretics are frequently referred to a water
pills. These medications are designed to
eliminate excess fluid and sodium from the
bloodstream, thus decreasing the overall pressure
within the vessels. Overuse or improper use can
lead to dehydration and kidney failure. Some of
the more common diuretics include furosemide.
32
Pharmacodynamic effects can be therapeutic,
diagnostic, or adverse. Diagnostic effects of
intravascular radiopaque contrast media (ROCM)
are a function of the iodine contained within
them. Adverse effects elicited by ROCM depend at
least partially on their serum or tissue iodine
concentration and osmolality and immune
systemstimulating abilities.
33
Serum iodine concentration must be within the
range of 280 to 370 mg/ml for a normal x-ray film
to reflect the vascular lumen. To achieve this
high iodine concentration, the ROCM must contain
a large proportion of iodine (see Chapter 6 for
iodine concentrations) and must be injected
intravascularly at a rate equal to or greater
than blood flow. If the contrast medium is
injected slowly, the cardiovascular system will
significantly dilute the iodine concentration
before imaging. Rapid intravascular injection
thus helps to limit the early dilutional effects
on the iodine by the cardiovascular system. High
concentrations of iodine pharmacodynamically
prevent the penetration of photons so that a
shadow is projected onto the radiographic
film. For computed tomography (CT) or digital
subtraction angiography (DSA), the serum iodine
concentration needs only to be between 2 and 8
mg/ml. Thus, either a less concentrated iodine
contrast medium or a slower intravascular
infusion will produce adequate pharmacodynamic
action for these imaging procedures.
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ANTICOAGULANT, ANTIPLATELET, AND THROMBOLYTIC
MEDICATIONS Patients receiving any of the
anticoagulant, antiplatelet, or thrombolytic
medications are at risk for bleeding. In some
cases, such as with the thrombolytics, severe
bleeding can to lead to hemorrhagic stroke.
Therefore, the imaging technologist should know
about the signs and symptoms of an evolving
stroke so that it can be reported quickly if
patients are taking one of these medications
35
Anticoagulant medication is frequently used in
patients who have either a history of blood clot
formation or the potential to develop blood
clots. Warfarin is an oral medication used to
prevent the absorption of vitamin K from the
intestinal tract, thus preventing the formation
of the blood-clotting factors responsible for the
propagation of a blood clot. Heparinis an
examples of medication that affect the activity
of thrombin in various ways to inhibit clot
formation. Antiplatelet medication is generally
used in patients who have experienced an acute
ischemic event to either their heart or their
brain in the past. Since platelets are one of the
initial instigators of blood clot formation,
cardiologists and neurologists will prescribe
antiplatelet drugs to prevent that portion of the
coagulation cascade. Aspirin is one of the most
common oral medications for inhibiting platelet
effects. Thrombolytic medication is used to
actively break up a newly formed clot, such as
found in patients with acute myocardial
infarction, acute stroke secondary to blood clot,
or lower leg ischemia. Alteplase, retaplase,
streptokinase, tenecteplase, and urokinase are
the most frequently used medications in this
class. If a patient has recently been given an
agent in this class, the patient is at very high
risk for bleeding internally and externally. Use
caution with all intravenous (IV) sites. Do not
start an IV line in these patients without
physician orders and close supervision.
36
ANALGESIC MEDICATIONS Analgesic medications are
prescribed more frequently than any other
medication on the market. The drugs are used to
treat both acute and chronic pain syndromes, such
as arthritis, headache, muscle sprains, cancer
pain, surgical and traumatic pain, nerve pain,
and in some cases, anxiety. Narcotic
medications stimulate central nervous system
receptors known as opioid receptors and cause a
decrease in the perception of pain. These are
very potent analgesics and are associated with
the potential for physical and psychological
addiction. The narcotic class of analgesic is
generally highly controlled by the local and
federal enforcement agencies to prevent
misappropriation into the community. The
narcotics are also dangerous in that respiratory
depression can rapidly occur to the point of
respiratory arrest if the dose is too great. The
technologist should keep this concept in mind if
patients are being treated with narcotic
medications. If respiratory arrest occurs,
naloxone is the drug of choice (given
intravenously, intramuscularly, or
endotracheally) to reverse immediately the
respiratory depressant effects of narcotic
agents. Examples of common narcotic medications
include morphine
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Aspirin went on sale as the first pharmaceutical
drug in 1899, after Felix Hoffman, a German
chemist at the drug company Bayer, successfully
modified salicylic acid, a compound found in
willow bark, to produce aspirin.
Acetaminophen is probably the most common
analgesic in use today. It is contained in almost
all pain medication combinations and is in a
subclass by itself. It is not fully known just
how acetaminophen elicits its effects, but some
believe that it acts by inhibiting prostaglandins
in the central nervous system that are
responsible for pain production. Acetaminophen is
a low-potency pain reliever and must not exceed
4000 mg per day because it is associated with
severe liver damage at high doses. Long-term use
of high doses can also cause renal and cardiac
damage.
38
ANTIHISTAMINE MEDICATIONS Antihistamines are
medications used to block histamine from
producing adverse effects such as itching,
inflammation, respiratory distress, and overall
allergic reactions. Common antihistamines include
hydroxyzine (Vistaril, Atarax) and
diphenhydramine (Benadryl).
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ENDOCRINE MEDICATIONS Diabetes and
hypothyroidism are two common endocrine problems
for which patients frequently receive drug
treatment. Antidiabetic medication is required
for patients who have difficulty maintaining
proper balance between blood sugar and tissue
sugar. Some patients are termed insulin dependent
(diabetes mellitus type 1) because they have
little or no circulating endogenous insulin.
Diabetic patients who have sufficient circulating
endogenous insulin but poor receptor sensitivity
to the insulin are termed noninsulin dependent
(diabetes mellitus type 2).
Technologists need to always be aware of patients
receiving metformin because this drug should be
held before and for at least 48 hours after
receiving a radiopaque contrast agent. If
metformin is not held, the patient is put at
increased risk for severe metabolic acidosis
secondary to metformin metabolite accumulation,
in the event renal dysfunction is caused by the
radiopaque contrast agent.
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ANTIINFECTIVE AGENTS Antibiotics are therapeutic
agents used to kill or suppress pathologic
microorganisms responsible for causing infectious
diseases. Antifungals are agents used to kill
mycotic (fungal) organisms, and antivirals are
used to suppress and limit the spread or shedding
of viruses that invade the human body. Generally,
these three medication subclasses act at the
cellular level to destroy, inhibit, or suppress
the cell wall, enzymatic activity, or ribosomal
or deoxyribonucleic acid (DNA) function of an
invading microorganism.
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CHEMOTHERAPY AGENTS Chemotherapy drugs are
extremely toxic compounds designed to kill off
rapidly growing (e.g., cancerous) cells of the
human body by altering or destroying the various
stages in cellular division. These agents are
toxic to all cells that are in a growth stage,
not only cancerous cells. Special precautions
should be taken with all chemotherapy patients so
that no medication touches the unexposed skin of
a health care worker. Coming into physical
contact with these medications can put the health
care worker at risk of serious side effects,
including the stimulation of a cancerous
condition. Even coming into contact with bodily
fluids into which the chemotherapy is secreted,
such as urine, can pose a potential threat to the
clinician. Universal precautions and special
gloves and gowns should be worn when dealing with
chemotherapy.
The rosy periwinkle plant, found in Madagascar,
is used to cure leukemia
42
RADIOPAQUE CONTRAST MEDIA Radiopaque contrast
media (ROCM) are high-density pharmacologic
agents used to visualize low-contrast tissues in
the body, such as the vasculature, kidneys,
gastrointestinal (GI) tract, and biliary
tree. The most frequently prescribed ROCM are
iodine and barium. The atomic number of iodine is
53, and the atomic number of barium is 56. Each
has a much higher atomic number and mass density
than the low-contrast tissues listed above. When
an iodinated compound fills a blood vessel or
when barium fills a portion of the GI tract,
these internal organs become visible on a
radiograph. Low-kilovoltage techniques (below 80
kilovoltage peak kVp) are usually selected to
produce high-contrast radiographs of the blood
vessels or genitourinary tract.
Higher-kilovoltage operation (above 90 kVp) is
used in GI examinations not only to reveal the
presence of the organ, but also to penetrate the
contrast media to see the walls and inner
structures.
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ADVERSE PHARMACODYNAMICS Serious adverse effects
from ROCM do occur. An estimated one of every
20,000 to 40,000 patients receiving ROCM dies as
a result of these effects. Although the odds of
death appear low, they become very real if it
happens to you or your patient. Thus, it is
paramount that the technologist understand
adverse effects so that proper actions can be
instituted as rapidly as possible.
44
ROCM are available in parenteral and enteral,
ionic and nonionic, and high-osmolality and
low-osmolality forms.
Iodine molecules contained within ROCM are
effective photon absorbers in the human body. The
iodine molecules essentially do not allow as many
photons to pass through for projection onto the
radiographic film. Thus, iodine molecules are
responsible for the silhouette images projected.
Radiopacity elicited by ROCM is a direct function
of the percentage of iodine (except in the case
of barium sulfate) in the molecule and the
concentration of media present. In the case of
barium sulfate, barium acts as iodine.
45
INTRAVASCULAR RADIOPAQUE CONTRAST
MEDIA Intravascular (i.e., intravenous or
intraarterial) ROCM are used to add density to
vascular structures. Increased density of the
media alters the attenuation of x-rays passing
through the area, thus enhancing the anatomic
image on the radiographic film.
Categories Three broad categories of
intravascular ROCM exist high-osmolality ionic,
low-osmolality nonionic, and low-osmolality ionic
ROCM. Generally, ionic ROCM exist in salt forms
consisting of sodium and meglumine whereas
nonionic ROCM are supplied as nonsalt forms.
High-osmolality ionic ROCM,contain three iodine
atoms per molecule and dissociate into two
osmotically active particles when injected into
the bloodstream. These particles consist of one
radiopaque anion (negatively charged particle)
and one cation (positively charged particle) for
every three iodine atoms in solution. The newer
low-osmolality nonionic ROCM, contain three
iodine atoms per molecule and do not dissociate
in solution
46
The newer low-osmolality ionic ROCM, consist of
six iodine atoms per molecule and dissociate into
two osmotically active particles. These are also
considered to be ratio-3.0 media because there
are six iodine atoms and two dissociated
particles per molecule for a ratio of 62, which
equals 31
47
Excretion Intravascular ROCM are excreted
primarily via the kidneys they are concentrated
in the kidneys and subsequently opacify the
entire renal system. Generally, renal parenchyma
is opacified first, followed by the tubular
structures, renal calyces, and pelvis, and ending
with the ureter and bladder. In normal renal
function, up to 100 of an intravascular dose is
excreted in 24 hours. A very small percentage may
be excreted into the intestines through the
hepatic-biliary system. Several days may be
required for complete excretion in patients with
renal impairment. Consequently, these patients
have much lower to no opacification in the
kidneys because up to 50 of the ROCM may be
eliminated via the hepatic-biliary system, thus
opacifying the biliary and GI tracts.
48
ENTERAL RADIOPAQUE CONTRAST MEDIA Enteral ROCM
are used to diagnose and evaluate disorders of
the GI system. These agents may also be used to
help define the cardiac shadow. Enteral ROCM can
be broken down into the categories of aqueous
solutions, suspensions, and tablets.
49
Solutions Diatrizoate meglumine and diatrizoate
sodium solutions are used for oral or rectal
administration to aid in the diagnosis of GI
tract disorders. Generally, these solutions are
used when barium sulfate suspension is
potentially harmful, such as in GI perforation.
The high osmolality of these agents causes
significant osmotic action within the GI tract.
This leads to significant dilution of the iodine
as well as a profuse diarrhea, systemic
hypovolemia, dehydration, and electrolyte
imbalance. Iodine dilution leads to less
definitive diagnostic studies this, along with
the adverse effect profile of iodine, is why
barium sulfate is often the preferred diagnostic
GI agent. The diatrizoate compounds are preferred
over barium sulfate for CT because of less
artifact production. Radiodensity (radiopacity)
occurs immediately in the esophagus and stomach
after oral administration but may take 15 to 90
minutes for the duodenum. Immediate radiodensity
occurs in the rectum and colon following rectal
administration. Gastrointestinal ROCM are not
absorbed through the GI wall and are thus
distributed solely into the GI lumen. These
agents are excreted by the GI tract into the
feces.
50
Suspensions Barium sulfate is an ROCM suspension
used for oral or rectal administration to aid in
the diagnosis of GI tract disorders. Barium is
radiodense in the same manner as iodine.
Radiodensity occurs immediately in the esophagus
and stomach after oral administration but may
take 15 to 90 minutes for the duodenum. Immediate
radiodensity occurs in the rectum and colon
following rectal administration. Barium sulfate
is generally the preferred GI ROCM because it
provides a more thorough visualization of
structures, especially the mucosa, without
extensive local adverse effects. Barium sulfate
may produce significant artifact in CT evaluation
of the GI tract and thus is not the preferred
agent for this radiologic examination. Barium
sulfate is not absorbed through the GI wall and
thus is distributed solely into the GI lumen. It
is excreted by the GI tract into the feces.
51
Tablets Iocetamic acid (Cholebrine) is an oral
ROCM used for opacifying the gallbladder.
Absorption varies from person to person, but the
gallbladder can generally be visualized
approximately 10 to 15 hours after oral
administration
Most of the iocetamic acid is excreted into the
urine 48 hours after administration. Some is
excreted via the biliary system into the feces.