Volumex Injection Dosage

Volumex (Iodinated I 131 Albumin Injection) is administered intravenously.

Parenteral drug products should be inspected visually for particulate matter and abnormal coloration prior to administration whenever solution and container permit.

Volumex (Iodinated I 131 Albumin Injection) may be colorless to very pale yellow. Solutions with excessive coloration should not be used.

When a procedure such as a blood volume or a circulation time determination is to be repeated, the total dosage administered in any one week should not exceed 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 Volumex and continuing for one or two weeks thereafter, is a suitable dose. Complete assay data for each single unit dose 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 radioactivity level. It is important to make certain that the radioactivity in the dose at the time of administration is sufficient for the intended use.

The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration.

Note: A shielded syringe may be used for withdrawing and injecting the iodinated I 131 albumin.

Total Blood and Plasma Volumes

Dosage may range from 5 to 50 microcuries.

Blood Volume Determination

A. Reference Solution

Reference solution is provided with each single unit dose of Volumex. 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. After withdrawing a background blood sample as described below, insert an intravenous (IV) line into a large vein in patient’s arm. Inject the entire Volumex dose (one milliliter) through the IV line for immediate delivery.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 US Nuclear Regulatory Commission or Agreement State regulations pertaining to the disposal of radioactive waste.
3. At 12, 18, 24, 30 and 36 minutes after injecting the dose, withdraw blood samples from the patient with a sterile syringe or evacuated sample tube containing anti-coagulant.

C. Calculation of Blood Volume

1. Take a known aliquot from each blood sample and determine radioconcentration in net cpm/mL.

2. Plot the 12, 18, 24, 30 and 36 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 12, 18, 24, 30 and 36 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 blood
Net cpm/mL patient’s blood sample x DF = 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 = 48,100

Net counts obtained from reference solution aliquot = 52, 430

If, for example, DF, dilution factor of the reference solution = 4000

Using the above formula gives = 52,430 x 4000 = 4360 mL

48,100

Serial Blood Volume Determinations

Iodinated I 131 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 131 albumin is injected.

Background Blood Sample

1. Withdraw background blood sample from large vein in patient’s sampling arm with a sterile syringe or evacuated sampling tube containing anti-coagulant.
2. Leaving needle in patient’s vein, detach syringe containing blood sample.
3. Attached syringe containing the dose of Volumex to the indwelling IV line 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 samples, and from the reference solution.
5. The radioconcentration (net cpm/mL) per aliquot of the background bloodsample must be subtracted from the radioconcentration per aliquot of the blood sample obtained after the injection of iodinated I 131 albumin. The formula for calculating each blood volume determination after the first one thus becomes:

Net cpm/mL reference solution blood x DF = blood

Net cpm/mL Net cpm/mL volume

postinjection minus background (in mL)

blood sample blood sample

Plasma Volume Determination

The 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 x DF = plasma

Net cpm/mL patient’s plasma sample volume

(in mL)

Protein Turnover Studies

Dosages used have ranged from 10 to 150 microcuries. After injection, a period of seven days should be allowed before determinations are made to permit the elimination of any degraded protein in the dose.

Radiation Dosimetry

The estimated absorbed radiation doses to an average patient (70 kg) from an intravenous injection of 50 microcuries of Iodinated I 131 Albumin Injection USP are shown in Table 4.

For doses of 10, 25, 75, 150, 500 and 750 microcuries, the estimated absorbed

doses are 0.2, 0.5, 1.5, 3, 10 and 15 times the number of rads given, respectively.