Technetium Tc99m Pyrophosphate for Heart Attack

INDICATIONS AND USAGE Technetium Tc 99m Pyrophosphate Injection is a bone imaging agent used to demonstrate areas of altered osteogenesis, and a cardiac imaging agent used as an adjunct in the diagnosis of acute myocardial infarction. Kit for the Preparation of Technetium Tc 99m Pyrophosphate Injection is a blood pool imaging agent which may be used for gated blood pool imaging and for the detection of sites of gastrointestinal bleeding. When reconstituted with sterile non-pyrogenic isotonic saline and administered intravenously 30 minutes prior to the intravenous administration of Sodium Pertechnetate Tc 99m Injection, approximately 76% of the injected radioactivity remains in the blood pool.

DOSAGE AND ADMINISTRATION After preparation with oxidant-free Sodium Pertechnetate Tc 99m Injection, the suggested dose range of Technetium Tc 99m Pyrophosphate Injection in the average ADULT patient (70 kg) is: Bone Imaging - 185-555 megabecquerels (5-15 mCi) Cardiac Imaging - 370-555 megabecquerels (10-15 mCi) The suggested dose range of the non-radioactive reconstituted Kit for the Preparation of Technetium Tc 99m Pyrophosphate Injection in the average ADULT patient (70 kg) is: Blood Imaging - Administer not less than one-third nor more than the total contents of one vial [555 - 740 megabecquerels (15-20mCi) of Pertechnetate Tc 99m Injection]. Bone and Cardiac Imaging Technetium Tc 99m Pyrophosphate Injection is injected intravenously over a 10 to 20 second period. For optimal results, bone imaging should be done 1 to 6 hours following administration. Cardiac imaging should be done 30 to 90 minutes following administration. The acute myocardial infarct can be visualized from 24 hours to 6 days following onset of symptoms, with maximum localization at 48 to 72 hours. Cardiac imaging should be done with a gamma scintillation camera. It is recommended that images be made of the anterior, left anterior oblique and left lateral projections. Blood Pool Imaging Kit for the Preparation of Technetium Tc 99m Pyrophosphate Injection may be reconstituted with sterile, non-pyrogenic isotonic saline containing no preservatives. Administer not less than one-third nor more than the total contents of one vial 30 minutes prior to the intravenous administration of 555 to 740 megabecquerels (15-20 mCi) Sodium Pertechnetate Tc 99m Injection. The non-radioactive reconstituted Kit for the Preparation of Technetium Tc 99m Pyrophosphate Injection should be injected by direct venipuncture. Heparinized catheter systems should be avoided. Cardiac imaging should be done 10 to 30 minutes following the administration of Sodium Pertechnetate Tc 99m Injection utilizing a scintillation camera interfaced to an electrocardiographic gating device. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration whenever solution and container permit. The patient dose should be measured by a suitable radioactivity calibration system immediately prior to administration. Radiation Dosimetry Bone and Cardiac Imaging The effective half-life was assumed to be the physical half-life for all calculated values. The estimated radiation absorbed doses to an average ADULT patient (70 kg) from an intravenous injection of a maximum of 555 megabecquerels (15 mCi) of Technetium Tc 99m Pyrophosphate Injection are shown in Table 4. TABLE 4: Estimated Absorbed Radiation Doses Bone and Cardiac Imaging* Technetium Tc 99m Pyrophosphate Injection Target Organ mGy/555 MBq rads/15 mCi Total Body 1.8 0.18 Kidneys 3.6 0.36 Red Marrow 3.5 0.35 Bone Surfaces 21.1 2.11 Bladder Wall 13.3 1.33 Testes 1.4 0.14 Ovaries 2.1 0.21 Effective Dose Equivalent 3.3 mSv 0.33 rem *Based on the model in MIRD Dose Estimate Report No. 13 (J Nucl Med 30:1117-1122, 1989). Estimate calculated using phantoms of Cristy & Eckerman (Report ORNL/TM-8381/V1 & V7). Bone and marrow model of Eckerman (Aspects of dosimetry of radionuclides within the skeleton with particular emphasis on the active marrow. In Fourth International Radiopharmaceutical Dosimetry Symposium; A.T. Schlafke-Stelson and E.E. Watson eds. CONF-851113, Oak Ridge Associated Universities, Oak Ridge, TN 37831, 1986. pp 514-534.) used. The effective dose equivalent is a quantity which may be suitable for comparing risks of different procedures in nuclear medicine, radiology, and other applications involving ionizing radiation, but should not be construed to give information about risks to individual patients and should not be applied to situations involving radiation therapy. Blood Pool Imaging The estimated absorbed radiation doses to an average adult patient (70 kg) from an intravenous injection of 740 megabecquerels (20 mCi) of Sodium Pertechnetate Tc 99m Injection, 30 minutes after the intravenous administration of the non-radioactive reconstituted Kit for the Preparation of Technetium Tc 99m Pyrophosphate Injection are shown in Table 5. TABLE 5: Estimated Absorbed Radiation Doses Blood Pool Imaging a Sodium Pertechnetate Tc 99m 30 min. Post Injection with Pyrophosphate Target Organ mGy/740 MBq rads/20 mCi Total Body 3.2 0.32 Spleen 3.6 0.36 Bladder Wall b 24.0 2.40 Testes 2.4 0.24 Ovaries 4.6 0.46 Blood 10.4 1.04 Red Marrow 4.4 0.44 a Assume 75% of the Sodium Pertechnetate Tc 99m labels red blood cells and the other 25% remains as pertechnetate. Method of calculation: MIRD Dose Estimate Report No. 8, J Nucl Med . 17: 74-77, 1976. b If 25% excreted with 1 hour T b

WARNINGS As an adjunct in the diagnosis of confirmed myocardial infarction (ECG and serum enzymes positive), the incidence of false negative images has been found to be 6 percent. False negative images can also occur if made prior to 24 hours in the evolutionary phase of the infarct or after 6 days in the resolution phase. In a limited study involving 22 patients in whom the ECG was positive and serum enzymes questionable or negative, but in whom the final diagnosis of acute myocardial infarction was made, the incidence of false negative images was 23 percent. The incidence of false positive images has been found to be 7 to 9 percent. False positive images have also been reported following coronary by-pass graft surgery, in unstable angina pectoris, old myocardial infarcts and in cardiac contusions. Preliminary reports indicate impairment of brain scans using Sodium Pertechnetate Tc99m Injection which have been preceded by a bone scan using an agent containing stannous ions. The impairment may result in false positive or false negative brain scans. It is recommended, where feasible, that brain scans precede bone imaging procedures. Alternately, a brain imaging agent such as Technetium Tc 99m Pentetate Injection may be employed. The biodistribution of technetium Tc 99m pyrophosphate may be altered in the presence of high levels of certain cations (iron, calcium, and aluminum). This may result in reduced uptake of radionuclide in the skeleton and increased extraosseal uptake, which may potentially degrade imaging quality. High levels of these cations may be caused by concomitant medications or medical conditions (e.g., iron overload, hypercalcemia, etc.). Most cases were observed after iron infusion. (See PRECAUTIONS, Drug Interactions .)

ADVERSE REACTIONS Some hypersensitivity reactions have been associated with pyrophosphate use.