TECHNETIUM TC-99M EXAMETAZIME: 28 Adverse Event Reports & Safety Profile

DESCRIPTION The Ceretec kit is supplied as a pack of 5 vials for use in the preparation of a technetium Tc99m exametazime intravenous injection as a diagnostic radiopharmaceutical for use as an adjunct in the detection of altered regional cerebral perfusion and for the radiolabeling of autologous leukocytes. Each vial of Ceretec contains a pre-dispensed sterile, non-pyrogenic, lyophilized mixture of 0.5 mg exametazime [(RR,SS)-4.8-diaza-3,6,6,9-tetramethylundecane-2, 10-dione bisoxime], 7.6 µg stannous chloride dihydrate (minimum stannous tin 0.6 µg; maximum total stannous and stannic tin 4.0 µg per vial) and 4.5 mg sodium chloride, sealed under nitrogen atmosphere with a rubber closure. The product contains no antimicrobial preservative. Prior to publication of the USAN, exametazime was formerly known as hexamethylpropylene amine oxime (HM-PAO). The name HM-PAO appears in many publications. The structural formula of exametazime is: When sterile pyrogen-free sodium pertechnetate Tc99m in isotonic saline is added to the vial of Ceretec, a Tc99m complex of exametazime is formed. Administration is by intravenous injection for diagnostic use.

Physical Characteristics

Technetium Tc99m decays by isomeric transition with a physical half-life of 6.03 hours. (1) Photons that are useful for imaging studies are listed in Table 1.

Table

1.

Principal Radiation Emission

Data-technetium Tc99m Radiation Mean %/ Disintegration Mean Energy (keV) (1) Dillman, L.T. and Von der Lage, F.C. Radionuclide decay schemes and nuclear parameters for use in radiation-dose estimation.

Mird

Phamphlet No. 10, p. 62, 1975.

Gamma

2 87.87

140.5 External Radiation The specific gamma ray constant for technetium Tc99m is 206 microCoulomb kg-1/37 MBq-h, (0.8 R/millicurie-h) at 1 cm. The first half-value thickness of lead (Pb) for technetium Tc99m is 0.2 mm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb is shown in Table 2. For example, the use of a 2.7 mm thickness of Pb will decrease the external radiation exposure by a factor of 1,000.

Table

2.

Radiation

Attenuation by Lead Shielding Shield Thickness (Pb) mm Coefficient of Attenuation 0.2 0.5 0.95 10 –1 1.8 10 –2 2.7 10 –3 3.6 10 –4 4.5 10 –5 To correct for physical decay of this radionuclide, the fractions that remain at selected intervals relative to the time of calibration are shown in Table 3.

Table

3.

Physical Decay

Chart: Tc99m half-life 6.03 hours Hours Fraction Remaining Hours Fraction Remaining 0 Calibration time (time of preparation) 1.000 7 0.447 1 0.891 8 0.399 2 0.795 9 0.355 3 0.708 10 0.317 4 0.631 11 0.282 5 0.563 12 0.252 6 0.502 24

0.063 Chemical Structure

AND USAGE Drax Exametazime is indicated for leukocyte (white blood cell) labeled scintigraphy as an adjunct in the localization of intra-abdominal infection and inflammatory bowel disease.

Drax

Exametazime is a radioactive diagnostic agent indicated for leukocyte (white blood cell) labeled scintigraphy as an adjunct in the localization of intra-abdominal infection and inflammatory bowel disease. ( 1 )

AND ADMINISTRATION Use careful handling with appropriate safety measures to minimize radiation exposure to both patients and healthcare professionals. ( 2.1 ) For an adult patient, recommended dose is 259 - 925 megabecquerels (MBq) [7-25 millicuries (mCi)]. ( 2.3 )

2.1 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 <span class="opacity-50 text-xs">[see Warnings and Precautions (5.3) ]</span> .

2.2 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 <span class="opacity-50 text-xs">[see Dosage and Administration ( 2.5 , 2.6 )]</span> . 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 <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.3 )]</span> .

2.3 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)].

2.4 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 )]

2.5 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.

2.7 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.

2.8 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 R f 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 R f 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 R f 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%

2.9 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

None. None. ( 4 )

REACTIONS The following adverse reactions are described elsewhere in the labeling; Hypersensitivity reactions [see Warnings and Precautions ( 5.1 )] . The following adverse reactions associated with the use of technetium Tc 99m exametazime have been identified in clinical trials or post-marketing reports. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Cardiovascular: transient blood pressure increase Skin and subcutaneous tissue disorders: rash, generalized erythema, urticaria, angioedema, pruritus. General disorders and administration site conditions: facial edema, fever, asthenic conditions (e.g., malaise, fatigue). Nervous system disorders: headache, dizziness, paraesthesia. Vascular disorders: flushing. Gastrointestinal disorders: nausea, vomiting. Most common adverse reactions include transient increase in blood pressure, rash, generalized erythema, facial edema and fever. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Jubilant DraxImage Inc. at 1-888-633-5343 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

AND PRECAUTIONS Hypersensitivity Reactions: Hypersensitivity reactions, including serious signs and symptoms of anaphylaxis, following administration of Tc 99m labeled leukocytes prepared using Tc 99m exametazime have been reported. Always have cardiopulmonary resuscitation equipment and personnel available and monitor all patients for hypersensitivity reactions. ( 5.1 )

5.1 Hypersensitivity Reactions Hypersensitivity reactions, including serious signs and symptoms of anaphylaxis, following administration of Tc 99m labeled leukocytes prepared using Tc 99m exametazime have been reported. Always have cardiopulmonary resuscitation equipment and personnel available and monitor all patients for hypersensitivity reactions.

5.2 Risk for Image Interpretation Error The interpretation of images can be affected by the presence of other pathophysiological processes within and outside of the abdominal cavity such as: tumor, infarction, trauma, and other inflammatory conditions.

5.3 Radiation Exposure Risk Technetium Tc 99m contributes to a patient’s overall long-term cumulative radiation exposure. Long-term cumulative radiation exposure is associated with an increased risk of cancer. Ensure safe handling and preparation reconstitution procedures to protect patients and health care workers from unintentional radiation exposure. Encourage patients to drink fluids and void as frequently as possible after administration <span class="opacity-50 text-xs">[see Dosage and Administration ( 2.1, 2.2 )]</span> .

PRECAUTIONS As with any injected product, acute hypersensitivity or allergic reactions are possible. Limited reports have been received of hypersensitivity reactions following administration of Tc99m labeled leukocytes prepared using Tc99m exametazime. However, the materials used in leukocyte cell separation may cause hypersensitivity reactions. It is essential that cells are washed free of sedimentation agents before they are reinjected into the patient. In case of side effects following administration of radiopharmaceuticals, users should ensure the availability of appropriate medical treatment at the time of administration of any radiopharmaceutical to the patient. A thorough knowledge of the normal distribution of intravenously administered technetium Tc99m exametazime injection is essential in order to interpret pathologic studies accurately. Caution should be exercised in making the final diagnosis. Results can be affected by the presence of tumor, infarction, peritonitis, non-gastrointestinal or bony sites of inflammatory cell collections. The contents of the Ceretec vial are not radioactive. After the sodium pertechnetate Tc99m is added, the product is radioactive and adequate shielding of the final preparation must be maintained. The contents of the Ceretec vial are intended only for use in preparation of technetium Tc99m exametazime injection and are NOT to be administered directly to the patient.

General

The contents of the Ceretec vial are sterile and pyrogen free. The vial contains no bacteriostatic preservative. It is essential that the user follow the directions carefully and adhere to strict aseptic procedures during preparation of the radiopharmaceutical. Radiopharmaceuticals should be used only by or under the control of physicians who are qualified by training and experience in the safe use and handling of radionuclides and whose experience and training have been approved by the appropriate governmental agency authorized to license the use of radionuclides. To minimize radiation dose to the bladder, the patient should be encouraged to void when the examination is completed and as often thereafter as possible. Adequate hydration should be encouraged to permit frequent voiding. Carcinogenesis, Mutagenesis, Impairment of Fertility Long term animal studies have not been performed to evaluate carcinogenic potential or whether exametazime affects fertility in males or females. When evaluated in the Ames test, exametazime increased the apparent rate of gene mutation in the TA100 strain of S. typhimurium. Exametazime did not cause chromosomal aberrations in vitro (Chinese Hamster Ovary cells) or in vivo (rat bone marrow).

Pregnancy

Category C Animal reproduction studies have not been conducted with Tc99m exametazime. It is also not known whether Tc99m exametazime can cause fetal harm when administered to a pregnant woman or if it can affect reproductive capacity. Therefore, Tc99m exametazime should not be administered to a pregnant woman unless the potential benefit justifies the potential risk to the fetus.

Nursing Mothers

Technetium Tc99m is excreted in human milk during lactation. It is not known whether exametazime is excreted in human milk. Therefore, formula feedings should be substituted for breast feeding for 60 hours.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

Geriatric Use

Clinical studies of Ceretec™ did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy. This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.