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Drax Exametazime Dosage

Generic name: TECHNETIUM TC-99M EXAMETAZIME 0.5mg
Dosage form: injection, powder, lyophilized, for solution

The information at Drugs.com is not a substitute for medical advice. Always consult your doctor or pharmacist.

Radiation Safety - Drug Handling

Technetium Tc 99m exametazime is a radioactive solution and should be handled with appropriate safety measures to minimize radiation exposure. During handling use waterproof gloves and effective shielding, including syringe shields [see Warnings and Precautions (5.3)].

Important Administration Instructions

  • Use strict aseptic procedures throughout preparation and handling.
  • Visually inspect the reconstituted technetium Tc 99m exametazime solution for particulate matter and discoloration prior to radiolabeling of white blood cells. Do not use the reconstituted solution if there is evidence of particulate matter or discoloration.
  • Follow the directions of drug preparation carefully to ensure efficient leukocytes labeling [see Dosage and Administration (2.5, 2.6)].
  • Measure patient dose with a suitable radioactivity calibration system immediately prior to administration.
  • Instruct patients to hydrate, after administration of technetium Tc 99m exametazime labeled white blood cells and void frequently to minimize radiation dose to the kidneys and bladder [see Warnings and Precautions (5.3)].

Recommended Dosage and Administration

For an adult patient the recommended intravenous injection dose range for technetium Tc 99m exametazime labeled leukocytes is 259 - 925 Megabecquerels (MBq) [7-25 millicuries (mCi)].

Image Acquisition and Inerpretation

Acquisition

  • Instruct patients to empty their bladder prior to imaging.
  • Obtain serial pelvic and abdominal images beginning at 0.5 – 1 hour post-injection and continue up to 4 hours.

Interpretation

  • Accumulation of radioactivity in bowel seen in early images [less than 4 hours] with increasing intensity and/or no evidence of changing location secondary to GI motility likely represents inflammatory bowel disease or infection. Radioactivity from hepatic excretion detected in the bowel 4 hours post-injection and changing in GI location on serial/subsequent images is indicative of normal GI transit [see Clinical Pharmacology (12.2)]

Preparation of Autologous Leukocytes

IMPORTANT - Label all syringes and tubes used in this labeling procedure with the patient’s name and unique identification number.

Leukocyte Harvest and Separation
1. Draw 2 mL of Heparin and 8 mL of 6% Hydroxyethyl starch into a 60 mL plastic syringe.
2. Withdraw approximately 40 mL whole blood from the patient into the syringe using a 19-gauge Butterfly needle infusion set. Close the syringe with a sterile hub.
3. Gently mix the contents for 2 minutes.
4. Clamp the syringe barrel to the ring stand in an upright (hub side up) position and tilt the syringe approximately 10-20 degrees from its position perpendicular to the bench.
5. Allow the syringe to stand a minimum of 60 minutes until the red blood cells sediment and the supernatant looks clear.
6. Using an infusion set, transfer the leukocyte-rich plasma (LRP), the supernatant, from the previous step, into a sterile, conical centrifuge tube marked "WBC" (white blood cell) and assure that only a minimum amount of red cells enter the centrifuge tube.
7. Immediately centrifuge the capped WBC tube at 400-450 g for 5 minutes. The plasma will separate out into a liquid [leukocyte poor plasma (LPP)] and a solid (WBC button). The WBC button often contains a small number of red blood cells and may appear red.
8. Transfer the leukocyte poor plasma (LPP) into another sterile centrifuge tube marked as "Plasma" tube, without disturbing the WBC button. Save the LPP in the Plasma tube for later use (Steps 16 and 19).

Red Blood Cell Lysis and Washing
9. Add 1 mL Sodium Chloride (Na Cl) Injection, USP (0.9%) to the WBC button and suspend.
10. Add the following to the WBC suspension in succession and swirl the centrifuge tube (WBC tube) for 5-30 seconds after each addition. (Attention to timing is important as exposing leukocytes to a hypotonic solution for a prolonged period will damage leukocytes and result in poor leukocyte labeling results):
a) 9 mL sterile water;
b) 2 mL of 5% Na Cl; and
c) 10 mL of 0.9% Na Cl.
11. Cap the WBC tube and centrifuge at 400 g for 5-7 minutes. Draw off the supernatant into the "Waste" tube.
12. Add 1.5 mL of 0.9% Na Cl and re-suspend the WBC button by gentle shaking.
13. Reconstitute technetium Tc 99m exametazime with generator eluate [see Dosage and Administration (2.7)]. Measure the radioactivity and record as item (1) on the Technetium Tc 99m Exametazime Labeling Efficiency Worksheet. Use for radiolabeling WBC within 30 minutes.

2.6 Labeling of Autologous Leukocytes with Technetium Tc 99m Exametazime

14. Carefully add the reconstituted technetium Tc 99m exametazime to the WBC tube containing the WBC button isolated in Step 12.
15. Incubate the WBCs at room temperature for 15 minutes. Swirl during the incubation every 5 minutes.
16. Add 5 mL of LPP (from Step 8) to the WBC tube. Cap the WBC tube and centrifuge at 400 g for 5 minutes.
17. Carefully remove the supernatant and place into the tube labeled “Wash.” Keep the labeled white cells in the WBC tube.
18. Measure the radioactivity of the Wash tube and record as item (2) on the Technetium Tc 99m Exametazime Labeling Efficiency Worksheet.
19. Add 5-10 mL of LPP (from Step 8) to the Tc 99m labeled leukocyte preparation (WBC tube). Gently swirl to mix.
20. Draw up the labeled cells into a non-heparinized syringe with a large bore needle (no smaller than 19-gauge) and cap it with a sterile hub. Measure the radioactivity of the cells and record as item (3) on the Technetium Tc 99m Exametazime Labeling Efficiency Worksheet.
21. Verify the identity of the leukocyte recipient.
22. Labeled cells are now ready for administration. Administer as soon as possible and preferably within 1-2 hours after labeling.
23. Calculate the labeling efficiency from the Labeling Efficiency Worksheet:

Radioactivity of the cells [item (3)]
Radioactivity of the cells [item (3)] + activity in the supernatant [item (2)]

Labeling efficiency >50% is anticipated.

Preparation of Technetium Tc 99m Exametazime

The technetium Tc 99m labeling reaction involved in preparing the agent depends on maintaining the stannous ion in the reduced state. Any oxidant present in the sodium pertechnetate Tc 99m may adversely affect the radiolabeling efficiency.

  • Elute the Tc 99m generator according to the manufacturer’s instructions.
    • Use only eluate from a Tc 99m generator which was eluted within the previous 24 hours.
    • Prepare the technetium Tc99m exametazime with eluate that is not more than 2 hours old.
  • Add 370 MBq up to 2000 MBq (10 mCi up to 54 mCi) sodium pertechnetate Tc 99m to Drax Exametazime vial.
  • Before reconstitution, add up to 5 mL preservative-free, non-bacteriostatic Sodium Chloride Injection USP (0.9%) to the generator eluate to achieve a radioactive concentration no greater than 74-370 MBq/mL (2-10 mCi/mL).
  • Measure the radioactivity and record as item (1) on the Technetium Tc 99m Exametazime Labeling Efficiency Worksheet.
  • Use a sample for Quality Control [see Dosage and Administration (2.8)].
  • Maintain reconstituted product at 20°C - 25°C (68°F - 77°F).
  • Use for WBC labeling within 30 minutes.
  • Discard any unused material according to local radiation safety procedures.

Radiochemical Purity Testing - Quality control of Tc 99m Exametazime

Obtain the Following Materials:
SG ITLC strips 6 cm x 0.7 cm
Whatman Grade 31ET chromatographic paper strip 6 cm x 0.7 cm
MEK (methyl ethyl ketone [butanone]) (99.9 + % HPLC Grade)
0.9% aqueous sodium chloride (non-bacteriostatic)
50% aqueous acetonitrile (99.9 + % HPLC Grade)
Glass test tubes (12 x 75 mm) with covers
1 mL syringes with 25-gauge needles.
Collimated radiation detector.

  • Perform radiochemical purity testing of technetium Tc 99m exametazime before leukocyte labeling and within 2 minutes of reconstitution.
  • This entire radiochemical purity testing procedure takes approximately 15 minutes.
  • A combination of 3 chromatographic systems is necessary for the complete definition of the radiochemical composition of the injection.
    • System 1: methyl ethyl ketone (MEK) + SG ITLC strip
    • System 2: 0.9% non-bacteriostatic sodium chloride solution + SG ITLC strip
    • System 3: 50% acetonitrile solution + Whatman 31ET paper strip
  • Three potential radiochemical impurities may be present in the prepared injection of the lipophilic Tc 99m exametazime complex:
    • secondary Tc 99m exametazime complex
    • free Tc 99m pertechnetate
    • reduced-hydrolyzed Tc 99m

Method
1. Prepare three chromatographic systems using 12 mm × 75 mm chromatographic tubes with the following solvents (identify the solvent in each tube):
System 1- 0.3 mL of fresh methyl ethyl ketone (MEK),
System 2 - 0.9% non-bacteriostatic sodium chloride solution,
System 3 - 50% acetonitrile solution, prepared with non-bacteriostatic water
2. Apply 5 µL of freshly prepared Tc 99m exametazime solution (within 2 minutes of reconstitution) about 1 cm from the bottom of three strips: two 6cm × 0.7cm instant thin-layer chromatographic strips and one 6 cm × 0.7cm strip of chromatographic paper. Do not allow to dry.
3. Place one SG ITLC strip into the MEK tube (System 1), the second SG ITLC strip into the saline tube (System 2) and the Whatman 31ET paper strip into the 50% acetonitrile tube (System 3). Make sure strips are not adhering to the sides of the tube.
4. Allow the chromatograms to develop until the solvent front has moved to the top of the strips. Remove the strips from the tubes, and allow the solvents to evaporate.
5. Determine the radioactive distribution by scanning the strip sections, using a suitable collimated radiation detector.

Chromatogram Interpretation
6. Using the Radiochemical Purity Worksheet, record the following counts:

System 1 (SG ITLC: MEK [butanone])
Migrate at Rf 0.8-1 Lipophilic Tc 99m exametazime complex and Tc 99m pertechnetate
Origin Secondary Tc 99m exametazime complex and reduced-hydrolyzed Tc 99m.
System 2 (SG ITLC: 0.9% sodium chloride)
Migrate at Rf 0.8-1 Tc 99m pertechnetate
Origin Lipophilic Tc 99m exametazime complex, secondary Tc 99m exametazime complex and reduced- hydrolyzed Tc 99m
System 3 (Whatman 31ET: 50% aqueous acetonitrile)
Migrate at Rf 0.8-1 Lipophilic Tc 99m exametazime complex, secondary Tc 99m exametazime complex and Tc 99m pertechnetate
Origin Reduced-hydrolyzed Tc 99m

7. Determine and record on the Radiochemical Purity Worksheet:
% at the origin of saline strip (D)
% at the origin of MEK strip (B)
% at the solvent front of saline strip (C) [% Tc 99m pertechnetate]
% at the origin of Whatman 31ET paper strip (F) [% reduced-hydrolyzed Tc 99m]

8. Calculate the radiochemical purity:
% lipophilic exametazime complex = % at the origin of saline strip (D) – % at the origin of MEK strip (B)

9. Do not use if radiochemical purity of Lipophilic Tc 99m Exametazime is less than 80%

Radiation Dosimetry

Based on human data, the radiation absorbed doses in an adult patient from an intravenous injection of Tc 99m labeled leukocytes have been estimated and are provided in Table 1.

Table 1 Tc 99m Exametazime Labeled Leukocytes
Organ Absorbed dose per unit activity administered Absorbed dose per unit activity administered
(microGy/MBq) (mrad/mCi)
Spleen 88 327
Red marrow 15 54
Liver 13 48
Bone surfaces 8.4 31
Urinary bladder 8.2 30
Lungs 7.4 27
Stomach 6.7 25
Upper large intestine 5.5 20
Colon 4.5 17
Lower large intestine 3.3 12
Small intestine 2.5 9.3
Ovaries 1.6 6
Thyroid 1.3 4.8
Breast 0.9 3.3
Testes 0.8 3
Kidneys 0.3 1.1
Remaining organs 2.2 8.1
Effective dose per administered activity 7.5 microSv/MBq 28 mrem/mCi

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