Following intravenous
injection, radioiodinated serum albumin is uniformly distributed
throughout the intravascular pool within 10 minutes; extravascular
distribution takes place more slowly. Labeled albumin also can be
detected in the lymph and in certain body tissues within 10 minutes
after injection, but maximum distribution of radioactivity
throughout the extravascular space does not occur until two to four
days after administration. The time at which extravascular activity
is maximal has been designated as the "equilibrium time."
When this point has been reached, the radioactivity remaining in
the intravascular and extravascular spaces decreases slowly and
exponentially in parallel fashion.The administered radioactivity is
climinated almost entirely in the urine, only about 2 percent of the
total dose ultimately appearing in the feces. The biologic half-life
of labeled albumin is dependent upon a number of factors, and
published studies have varied considerably in their reporting of
this figure. It has ranged, in the literature, from below 10 days to
20 days. One important factor affecting the biologic half-life is
the initial rate of excretion, and this depends in part on the
quality of the labeled albumin. With Jeanatope I-125 the biologic
half-life in normal individuals has been reported to be
approximately 14 days.
INDICATIONS AND USAGE
Jeanatope I-125 is indicated for
use in the determination of total blood and plasma volume.
CONTRADICTIONS
At present there are no known
contraindications to the use of the preparation.
WARNINGS
Radiopharmaceuticals should not be
administered to patients who are pregnant or to nursing mothers
unless the expected benefit to be gained outweighs the potential
hazards.Since I-125 is excreted in human milk during lactation,
formula-feedings should be substituted for breast-feedings.Ideally,
examinations using radiopharmaceuticals, especially those elective
in nature, of a woman of childbearing capability should be performed
during the first few (approximately 10) days following the onset of
menses.A few instances of hyperpyrexia and aseptic (chemical)
meningeal irritation have been reported with the use of this
reported with the product in cisternography. This material is not
approved for use in cisternography.
PRECAUTIONS
In the use of any radioactive material,
care should be taken to insure minimum radiation exposure to the
patient and occupational workers consistent with proper patient
management.
ADVERSE REACTIONS
Although the immunological properties
of serum albumin are believed to be virtually unaltered by the
iodination process, there is a theoretical possibility that allergic
reactions may occur in patients receiving additional doses a number
of weeks after an initial dose.
DOSAGE AND ADMINISTRATION
Radioiodinated serum
albumin is administered intravenously. When a procedure such as
blood volume determination is to be repeated, the total dosage
administered in any one week should not exceed 7.4 megabecquerels
(200 microcuries).To minimize the uptake of radioactive iodine by
the thyroid, prior administration of Lugol 's Solution
(Strong Iodine Solution USP) may be used. Ten drops of
Lugol's Solution three times daily, beginning at least 24
hours before administration of Iodinated Serum Albumin I-125 and
continuing for one or two weeks thereafter, is a suitable
dose.Complete assay data for each vial are provided on the
container.
Note: The expiration date given on the container pertains
to the biologic properties of the material and not to the
radioactive level, it is important to make certain that the
radioactivity in the dose at the time of administration is
sufficient for the intended use.
Visual Inspection. Parental drug products should be
inspected visually for particulate matter and discoloration prior to
administration, whenever solution and container permit.
Jeanatope (Iodinated I-125 Albumin injection) may be colorless to
very pale yellow. Solutions with excessive coloration should not be
used.The patient dose should be measured by a suitable radioactivity
calibration system immediately prior to administration.
Note: A shielded syringe should be used for withdrawing
and injecting the Iodinated I-125 Albumin.
Total Blood and Plasma Volumes
Dosage may range from
.185 to 1.85 megabecquerels (5 to 50 microcuries).
Blood Volume Determination
A. Preparation of Reference
Solution
Remote an aliquot of the vial to be used in the
procedure identical in volume to the dose to be administered to the
patient. Prepare a reference solution using normal saline as a
diluent. The recommended dilution is 1:4000 (Dilution Factor (DF) =
4000). Determine the radioactivity concentration (net cpm/mL) of the
reference solution. Care must be taken to assure that the reference
solution and the blood samples (Step B3) are assayed using the same
geometric configuration.
B. Administration of Dose
1.
Inject the dose into a large vein in patient's arm. Measure
the residual radioactivity in the syringe and needle.
2. Destroy
syringe after injecting. Do not attempt to resterilize.
CAUTION: the syringe should be disposed of in accordance
with the U.S. Nuclear Regulatory Commission or Agreement State
regulations pertaining to the disposal of radioactive waste.
3.
At 5 to 15 minutes after injecting the dose, withdraw blood samples
from the patient's other arm with a sterile
heparinized syringe.
C. Calculation of Blood Volume
1.
Take a known aliquot from each blood sample and determine
radioconcentration in net cpm/mL.
2. Plot the 5- and 15-minute
sample counts (net cpm/mL) on semilog graph paper using the average
count value of each sample and determine the radioconcentration at
injection time (zero time) by drawing a straight line through the
15- and 5-minute points to zero time. The x ordinate of the graph is
the sample withdrawal time and the logarithmic y ordinate is
radioconcentration in net cpm/mL.
3. Calculate patient's
blood volume (in mL) using the following formula:
(Net cpm/mL
reference solution / Net cpm/mL patient' s blood sample) x DF
= blood volume (in mL)
Sample Blood Volume
Calculations
Volume of blood sample aliquot
=
1.0 mL
Volume of reference solution aliquot
=
1.0 mL
Net counts at zero time
=
2500
Net counts obtained from reference solution aliquot
= 2725
Using the formula above gives (2725/2500) x
4000 = 4360 mL.
Serial Blood Volume
Determinations
Jeanatope (Iodinated I-125 Albumin Injection)
is administered in sufficiently low dosage to permit repetitions as
often as required by clinical circumstances. It must be remembered
that it is always necessary to correct for background radioactivity
remaining in the blood from former determinations. Therefore, for
each determination after the first one, a background blood sample
must be taken just before the Iodinated I-125 Albumin is
injected.
Background Blood Sample
1. Prior to
injecting Jeanatope I-125, withdraw background blood sample from
large vein in patient's arm with a sterile heparinized
syringe.
2. Leaving needle in patient 's vein, detach
syringe containing blood sample.
3. Withdraw Jeanatope I-125
from the vial and administer (see instructions under Blood Volume
Determination, Administration of Dose).
4. Determine
radioconcentration in net cpm/mL of aliquots taken from background
and postinjection blood samplers, and from the reference
solution. The radioconcentration (net cpm/mL) per aliquot of
the background blood sample must be subtracted from the
radioconcentration per aliquot of the blood sample obtained
after the injection of Iodinated I-125 Albumin. The formula
for calculating each blood volume determination after the first one
thus becomes:
[Net cpm/mL reference solution / (Net cpm/mL
postinjection blood sample - Net cpm/mL background blood sample)] x
400 = blood volume (in mL)
Plasma Volume DeterminationThe
procedure is essentially the same as that for blood volume
determination, except that the blood sample drawn from the patient
is centrifuged, the red blood cells are removed, and net cpm/mL of
the plasma is determined. The formula for calculation of plasma
volume, therefore is:
(Net cpm/mL reference solution / Net cpm/mL
patient 's plasma sample) x 400 = plasma volume (in
mL)
Radiation DosimetryThe estimated absorbed radiation
doses to an average patient (70 kg) from an intravenous injection of
1.85 megabecquerels (50 microcuries) of Iodinated I-125 Albumin USP
are shown in
