Nonionic iodinated contrast media inhibit
blood coagulation, in vitro, less than ionic contrast
media. Clotting has been reported when blood remains in contact with
syringes containing nonionic contrast media.
Serious, rarely fatal, thromboembolic events causing
myocardial infarction and stroke have been reported during angiographic
procedures with both ionic and nonionic contrast media. Therefore,
meticulous intravascular administration technique is necessary, particularly
during angiographic procedures, to minimize thromboembolic events.
Numerous factors, including length of procedure, catheter and syringe
material, underlying disease state, and concomitant medications may
contribute to the development of thromboembolic events. For these
reasons, meticulous angiographic techniques are recommended including
close attention to guidewire and catheter manipulation, use of manifold
systems and/or three way stopcocks, frequent catheter flushing with
heparinized saline solutions, and minimizing the length of the procedure.
The use of plastic syringes in place of glass syringes has been reported
to decrease but not eliminate the likelihood of in vitro clotting.
Caution must be exercised
in patients with severely impaired renal function, those with combined
renal and hepatic disease, or anuria, particularly when larger or
repeat doses are administered.
Radiopaque diagnostic contrast agents are potentially hazardous in
patients with multiple myeloma or other paraproteinemia, particularly
in those with therapeutically resistant anuria. Myeloma occurs most
commonly in persons over age 40. Although neither the contrast agent
nor dehydration has been proved separately to be the cause of anuria
in myelomatous patients, it has been speculated that the combination
of both may be causative. The risk in myelomatous patients is not
a contraindication; however, special precautions are required.
Contrast media may promote sickling in
individuals who are homozygous for sickle cell disease when injected
intravenously or intraarterially.
Administration of radiopaque materials to patients known or suspected
of having pheochromocytoma should be performed with extreme caution.
If, in the opinion of the physician, the possible benefits of such
procedures outweigh the considered risks, the procedures may be performed;
however, the amount of radiopaque medium injected should be kept to
an absolute minimum. The blood pressure should be assessed throughout
the procedure and measures for treatment of a hypertensive crisis
should be available. These patients should be monitored very closely
during contrast enhanced procedures.
Reports of thyroid storm following the use of iodinated
radiopaque diagnostic agents in patients with hyperthyroidism or with
an autonomously functioning thyroid nodule suggest that this additional
risk be evaluated in such patients before use of any contrast medium.
Severe Cutaneous Adverse
Reactions: Severe cutaneous adverse reactions (SCAR) may develop
from 1 hour to several weeks after intravascular contrast agent administration.
These reactions include Stevens-Johnson syndrome and toxic epidermal
necrolysis (SJS/TEN), acute generalized exanthematous pustulosis (AGEP)
and drug reaction with eosinophilia and systemic symptoms (DRESS).
Reaction severity may increase and time to onset may decrease with
repeat administration of contrast agent; prophylactic medications
may not prevent or mitigate severe cutaneous adverse reactions. Avoid
administering Isovue to patients with a history of a severe cutaneous
adverse reaction to Isovue.
Diagnostic procedures
which involve the use of any radiopaque agent should be carried out
under the direction of personnel with the prerequisite training and
with a thorough knowledge of the particular procedure to be performed.
Appropriate facilities should be available for coping with any complication
of the procedure, as well as for emergency treatment of severe reaction
to the contrast agent itself. After parenteral administration of a
radiopaque agent, competent personnel and emergency facilities should
be available for at least 30 to 60 minutes since severe delayed reactions
may occur. Caution should be exercised in hydrating patients with
underlying conditions that may be worsened by fluid overload, such
as congestive heart failure.
Diabetic nephropathy may predispose to acute renal impairment following
intravascular contrast media administration. Acute renal impairment
following contrast media administration may precipitate lactic acidosis
in patients who are taking biguanides.
The administration of iodinated contrast media may
aggravate the symptoms of myasthenia gravis.
Preparatory dehydration is dangerous and may contribute
to acute renal failure in patients with advanced vascular disease,
diabetic patients, and in susceptible nondiabetic patients (often
elderly with preexisting renal disease). Patients should be
well hydrated prior to and following iopamidol administration. The possibility of a reaction, including serious, life-threatening,
fatal, anaphylactoid or cardiovascular reactions, should always be
considered (see ADVERSE REACTIONS). Patients at increased risk include those with a history of a previous
reaction to a contrast medium, patients with a known sensitivity to
iodine per se, and patients with a known clinical hypersensitivity
(bronchial asthma, hay fever, and food allergies). The occurrence
of severe idiosyncratic reactions has prompted the use of several
pretesting methods. However, pretesting cannot be relied upon to predict
severe reactions and may itself be hazardous for the patient. It is
suggested that a thorough medical history with emphasis on allergy
and hypersensitivity, prior to the injection of any contrast medium,
may be more accurate than pretesting in predicting potential adverse
reactions. A positive history of allergies or hypersensitivity does
not arbitrarily contraindicate the use of a contrast agent where a
diagnostic procedure is thought essential, but caution should be exercised.
Premedication with antihistamines or corticosteroids to avoid or minimize
possible allergic reactions in such patients should be considered.
Recent reports indicate that such pretreatment does not prevent serious
life-threatening reactions but may reduce both their incidence and
severity.
Pre-existing conditions,
such as pacemakers or cardiac medications, specifically beta-blockers,
may mask or alter the signs or symptoms of an anaphylactoid reaction,
as well as masking or altering the response to particular medications
used for treatment. For example, beta-blockers inhibit a tachycardiac
response, and can lead to the incorrect diagnosis of a vasovagal rather
than an anaphylactoid reaction. Special attention to this possibility
is particularly critical in patients suffering from serious, life-threatening
reactions.
General anesthesia
may be indicated in the performance of some procedures in selected
patients; however, a higher incidence of adverse reactions has been
reported with radiopaque media in anesthetized patients, which may
be attributable to the inability of the patient to identify untoward
symptoms, or to the hypotensive effect of anesthesia which can reduce
cardiac output and increase the duration of exposure to the contrast
agent.
Even though the osmolality
of iopamidol is low compared to diatrizoate or iothalamate based ionic
agents of comparable iodine concentration, the potential transitory
increase in the circulatory osmotic load in patients with congestive
heart failure requires caution during injection. These patients should
be observed for several hours following the procedure to detect delayed
hemodynamic disturbances. Injection site pain and swelling may occur.
In the majority of cases it is due to extravasation of contrast medium.
Reactions are usually transient and recover without sequelae. However,
inflammation and even skin necrosis have been seen on very rare occasions.
In angiographic procedures, the possibility
of dislodging plaques or damaging or perforating the vessel wall,
or inducing vasospasm, and or subsequent ischemic events, should be
borne in mind during catheter manipulations and contrast medium injection.
Test injections to ensure proper catheter placement are suggested.
Selective coronary arteriography should
be performed only in selected patients and those in whom the expected
benefits outweigh the procedural risk. The inherent risks of angiocardiography
in patients with pulmonary hypertension must be weighed against the
necessity for performing this procedure. Angiography should be avoided
whenever possible in patients with homocystinuria, because of the
risk of inducing thrombosis and embolism. See also Pediatric Use.
In addition to the general precautions previously described,
special care is required when venography is performed in patients
with suspected thrombosis, phlebitis, severe ischemic disease, local
infection or a totally obstructed venous system. Extreme caution during
injection of contrast media is necessary to avoid extravasation and
fluoroscopy is recommended. This is especially important in patients
with severe arterial or venous disease.
Parenteral drug products should be inspected
visually for particulate matter and discoloration prior to administration,
whenever solution and container permit. Iopamidol solutions should
be used only if clear and within the normal colorless to pale yellow
range. Discard any product which shows signs of crystallization or
damage to the container-closure system, which includes the glass container,
stopper and/or crimp.
It is
desirable that solutions of radiopaque diagnostic agents for intravascular
use be at body temperature when injected. Withdrawal of contrast agents
from their containers should be accomplished under aseptic conditions
with sterile syringes. Sterile techniques must be used with any intravascular
injection, and with catheters and guidewires.
Patients should be well hydrated prior
to and following ISOVUE (lopamidol Injection) administration.
As with all radiopaque
contrast agents, only the lowest dose of ISOVUE necessary to obtain
adequate visualization should be used. A lower dose reduces the possibility
of an adverse reaction. Most procedures do not require use of either
a maximum dose or the highest available concentration of ISOVUE; the
combination of dose and ISOVUE concentration to be used should be
carefully individualized, and factors such as age, body size, size
of the vessel and its blood flow rate, anticipated pathology and degree
and extent of opacification required, structure(s) or area to be examined,
disease processes affecting the patient, and equipment and technique
to be employed should be considered.