Megatope

Megatope Manufacturers

• Iso-tex Diagnostics, Inc.
  

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  Megatope | Iso-tex Diagnostics, Inc.

  

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  Megatope  (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.

  Megatope (Iodinated I 131 Albumin Injection) may be colorless to very pale yellow. 

  Solutions with excessive colorations should not be used.

      When a procedure such as 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 

  Megatope 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 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 should 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. Preparation of Reference Solution

  Remove an aliquot of the contents 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.

  A. 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 the 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 5 and 15 minutes after injecting the dose, withdraw blood samples from the

      patient's other arm with a sterile heparinized syringe.

  B. 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 iof the graph is the sample

      withdrawal time and the logarithmic y ordinate is radioconcentration in

      net cpm/mL.

  3. Calculate the patient's blood volume (in mL) using the following formula:

        Net cpm/mL reference solution               ×    DF = blood volume (in mL)

     Net cpm/mL patient's blood sample

  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

  Using the formula above 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 arm with a sterile

      heparinized syringe.

  2. Leaving needle in patient's vein, detach syringe containing blood sample.

  3. Attach syringe containing the dose of Megatope to the indwelling needle 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.

     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 131 albumin. The formula for calculating

  each blood volume determination after the first one thus becomes:

       Net cpm/mL reference solution           ×  DF    =        blood
  Net cpm/mL                       Net cpm/mL                       volume
  postinjection     minus         background
  blood sample                     blood sample                      (in mL)

  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                ×     DF    =   plasma volume
    Net cpm/mL patient's plasma sample                                   (in mL)

  Cardiac Output

  Dosage generally ranges from 3 to 50 microcuries.

  Cardiac and Pulmonary Blood Volumes; Circulation Times

  Dosages used have generally been 75 to 130 microcuries.

  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.

  Heart and Great Vessel Delineation

  The suggested dosage is 5 microcuries per kg of body weight, although doses up to

  750 microcuries have been used, depending on the instrumentation available and the

  scanning technique employed.

  Localization of the Placenta

  For localization of the placenta in the differential diagnosis of placenta praevia, a 3 to 5

  microcurie dose is recommended; this dose has proved adequate for excellent

  localization, and the fetal total body radiation is a fraction of that received during x-ray

  placentography. While fetal thyroid irradiation is higher with Iodinated I 131 Albumin

  Injection than with x-ray placentography, the administration of Lugol's Solution is

  reported to eliminate this hazard.

  Localization of Celebral Neospasms

  The suggested dosage is 5 microcuries per kg of body weight. Although doses as

  large as 500 microcuries of Iodinated I 131 Albumin Injection have been used, the

  dose should be kept as small as possible. Dosage is administered six hours before the

  initial examination, and scans are repeated at periodic intervals.

  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.

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